How did oxytonic come to mean “final accent” rather than “acute accent”?

Question

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.

(ˈɒksɪtəʊn)

Also oxyton.

[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”?

Answer 1

As the OED notes, this is an originally Greek term applicable to Greek grammar primarily. An 1871 Oxford UP abridgement of the Liddell-Scott Greek Lexicon defines it thus:

ὀξύτονος, ον (ὀξύς, τόνος) stretched to a point : sharp, piercing : violent. II. having the acute accent, i.e., accent on the last syllable, oxytone.

Granted, that "i.e." fails to explain the transition in meaning. The full modern Liddell-Scott-Jones Lexicon is even less helpful.

Classical Greek words have five basic accent classes: oxytones have acute accent on the ultima (final syllable), paroxytones on the penult (next-to-last), proparoxytones on the antepenult (third-to-last); perispomena have circumflex accent on the ultima, properispomena on the penult. Thus the oxytone is actually not the only class with accent on the ultima. The acute accent on the ultima of an oxytone routinely becomes grave when another word follows, but it remains an oxytone. These accents probably had more to do with pitch than loudness when they first appeared in Hellenistic times, though in modern Greek they are stress accents, and have generally resolved down to a single kind, termed οξεία.

The application of this terminology to Japanese is presumably merely a matter of rough equivalency, like calling the English subjective, objective, and possessive cases "nominative," "accusative," and "genitive" respectively, or applying the term "gender" to the Algonquian grammatical distinction between animate and inanimate nouns.