In the opening chapter of De Musica (written 387-391), St. Augustine gives an example of a Latin oxytone, i.e. a word with accentual stress on the ultimate syllable:
MASTER: Now when we pronounce the verb ‘pōne’ and the adverb ‘pōne’, except for the difference in meaning, do you perceive no difference in sound?
DISCIPLE: There is quite a difference.
MASTER: What is the difference, since both consist of the same times and the same letters?
DISCIPLE: The difference is they have the acute accent in different places.
Latin text:
M. Quid? cum enuntiamus, ‘pone’ verbum, et ‘pone’ adverbium; praeter id quod significatio diversa est, nihil tibi videtur sonus distare?
D. Distat omnino.
M. Unde distat, cum et iisdem temporibus utrumque, et iisdem litteris constet?
D. Eo distat quod in diversis locis habent acumen.
What's going on here? Why would the adverb 'pōne' be pronounced poné rather than póne? I read in this answer that it's an exception to the rule of accent-always-on-the-penult-or-antepenult, and applies to certain other adverbs too (or at least it did in the fourth century):
... ancient grammarians insisted on oxytone stress in some conjunctions: pone (after), sine, ergo, verum (but), in some cases arguably to distinguish those from other homophones. Mancini 1997, however, seems to dispute this.
What is the reasoning behind it? Is it a shift in grammatical prescription, or was it always that way? Is it due to some etymological development of those particular words? I am also looking for particular sources to cite — down to page number if possible — to convince others who might ask, especially since this is scarcely mentioned in Latin language classes.
