Unless one is a professional philologist he feels little interest in the language of the common people. Its peculiarities in pronunciation, syntax, phraseology, and the use of words we are inclined to avoid in our own speech, because they mark a lack of cultivation. We test them by the standards of polite society, and ignore them, or condemn them, or laugh at them as abnormal or illogical or indicative of ignorance. So far as literature goes, the speech of the common people has little interest for us because it is not the recognized literary medium. These two reasons have prevented the average man of cultivated tastes from giving much attention to the way in which the masses speak, and only the professional student has occupied himself with their language. This is unfortunate because the speech of the common people has many points of interest, and, instead of being illogical, is usually much more rigid in its adherence to its own accepted principles than formal speech is, which is likely to be influenced by convention or conventional associations. To take an illustration of what I have in mind, the ending -s is the common mark in English of a plural form. For instance, "caps," "maps," "lines," and "places" are plurals, and the corresponding singular forms are "cap," "map," "line," and "place." Consequently, granted the underlying premise, it is a perfectly logical and eminently scientific process from the forms "relapse" (pronounced, of course, "relaps") and "species" to postulate a corresponding singular, and speak of "a relap" and "a specie," as a negro of my acquaintance regularly does. "Scrope" and "lept," as preterites of "scrape" and "leap," are correctly formed on the analogy of "broke" and "crept," but are not used in polite society.
So far as English, German, or French go, a certain degree of general interest has been stimulated lately in the form which they take in every-day life by two very different agencies, by the popular articles of students of language, and by realistic and dialect novels. But for our knowledge of the Latin of the common people we lack these two all-important sources of information. It occurred to only two Roman writers, Petronius and Apuleius, to amuse their countrymen by writing realistic stories, or stories with realistic features, and the Roman grammarian felt an even greater contempt for popular Latin or a greater indifference to it than we feel to-day. This feeling was shared, as we know, by the great humanists of the fourteenth and fifteenth centuries, when the revival of interest in the Greek and Latin languages and literatures begins. Petrarch, Poggio Bracciolini, and the other great leaders in the movement were concerned with the literary aspects of the classics, and the scholars of succeeding generations, so far as they studied the language, confined their attention to that of the great Latin stylists. The first student to conceive of the existence of popular Latin as a form of speech which differed from formal literary Latin, seems to have been the French scholar, Henri Étienne. In a little pamphlet on the language and style of Plautus, written toward the end of the sixteenth century, he noted the likeness between French and the language of the Latin dramatist, without, however, clearly perceiving that the reason for this similarity lay in the fact that the comedies of Plautus reflect the spoken language of his time, and that French and the other Romance languages have developed out of this, rather than from literary Latin. Not until the middle of the eighteenth century was this truth clearly recognized, and then almost simultaneously on both sides of the Rhine.
It was left for the nineteenth century, however, to furnish scientific proof of the correctness of this hypothesis, and it was a fitting thing that the existence of an unbroken line of connection between popular Latin of the third century before our era, and the Romance languages of the nineteenth century, should have been established at the same time by a Latinist engaged in the study of Plautus, and a Romance philologist working upward toward Latin. The Latin scholar was Ritschl, who showed that the deviations from the formal standard which one finds in Plautus are not anomalies or mistakes, but specimens of colloquial Latin which can be traced down into the later period. The Romance philologist was Diez, who found that certain forms and words, especially those from the vocabulary of every-day life, which are common to many of the Romance languages, are not to be found in serious Latin literature at all, but occur only in those compositions, like comedy, satire, or the realistic romance, which reflect the speech of the every-day man. This discovery made it clear that the Romance languages are related to folk Latin, not to literary Latin. It is sixty years since the study of vulgar Latin was put on a scientific basis by the investigations of these two men, and during that period the Latinist and the Romance philologist have joined hands in extending our knowledge of it. From the Latin side a great impetus was given to the work by the foundation in 1884 of Wölfflin's Archiv für lateinische Lexikographie und Grammatik. This periodical, as is well known, was intended to prepare the way for the publication of the Latin Thesaurus, which the five German Academies are now bringing out.
One of its primary purposes, as its title indicates, was to investigate the history of Latin words, and in its first number the editor called attention to the importance of knowing the pieces of literature in which each Latin word or locution occurred. The results have been very illuminating. Some words or constructions or phrases are to be found, for instance, only in comedy, satire, and the romance. They are evidently peculiar to vulgar Latin. Others are freely used in these types of literature, but sparingly employed in historical or rhetorical works. Here again a shade of difference is noticeable between formal and familiar usage. The method of the Latinist then is essentially one of comparison and contrast. When, for instance, he finds the word equus regularly used by serious writers for "horse," but caballus employed in that sense in the colloquial compositions of Lucilius, Horace, and Petronius, he comes to the conclusion that caballus belongs to the vocabulary of every-day life, that it is our "nag."
The line of reasoning which the Romance philologist follows in his study of vulgar Latin is equally convincing. The existence of a large number of words and idioms in French, Spanish, Italian, and the other Romance languages can be explained only in one of three ways. All these different languages may have hit on the same word or phrase to express an idea, or these words and idioms may have been borrowed from one language by the others, or they may come from a common origin. The first hypothesis is unthinkable. The second is almost as impossible. Undoubtedly French, for instance, borrowed some words from Spanish, and Spanish from Portuguese. It would be conceivable that a few words originating in Spain should pass into France, and thence into Italy, but it is quite beyond belief that the large element which the languages from Spain to Roumania have in common should have passed by borrowing over such a wide territory. It is clear that this common element is inherited from Latin, out of which all the Romance languages are derived. Out of the words, endings, idioms, and constructions which French, Spanish, Italian, and the other tongues of southern Europe have in common, it would be possible, within certain limits, to reconstruct the parent speech, but fortunately we are not limited to this material alone. At this point the Latinist and the Romance philologist join hands. To take up again the illustration already used, the student of the Romance languages finds the word for "horse" in Italian is cavallo, in Spanish caballo, in French cheval, in Roumanian cal, and so on. Evidently all these forms have come from caballus, which the Latinist finds belongs to the vocabulary of vulgar, not of formal, Latin. This one illustration out of many not only discloses the fact that the Romance languages are to be connected with colloquial rather than with literary Latin, but it also shows how the line of investigation opened by Diez, and that followed by Wölfflin and his school, supplement each other. By the use of the methods which these two scholars introduced, a large amount of material bearing on the subject under discussion has been collected and classified, and the characteristic features of the Latin of the common people have been determined. It has been found that five or six different and independent kinds of evidence may be used in reconstructing this form of speech.