In Samuel Martin's Reference Grammar of Japanese (1975), the author describes the location of lexical accent on Japanese words using the following terms:
- Prototonic: The accent is at the beginning of the word.
- Mesotonic: The accent is somewhere in the middle of the word.
- Oxytonic: The accent is at the end of the word.
Prototonic and mesotonic seem clear enough to me, literally meaning something like “beginning tone” and “medial tone”. But oxytonic is less obvious to me. It seems like it should mean something like “final tone”, but when I look up oxy- in dictionaries I instead find something like “sharp, acute”.
This is explained somewhat in The Oxford English Dictionary in the definition for oxytone:
oxytone, a. and n. Gram., chiefly Gr. Gram.
[ad. Gr. ὀξύτον-ος having the acute accent, f. ὀξυ- sharp, acute + τόνος pitch, tone, accent.]
a. adj. Having an acute accent on the last syllable. b. n. A word so accented.
So it seems that oxy- refers to an “acute” accent. But I must confess it's still not entirely clear to me. How did this word come to be used for an acute accent on the final syllable specifically? Weren't acute accents used historically on non-final syllables as well? Was there a language where acute accents only fell on final syllables?
In short, how did oxytonic come to mean “final accent” rather than “acute accent”?