"agreement in terminal sounds," 1565, partially restored spelling, from M.E.
ryme, rime (c.1200) "measure, meter, rhythm," later "rhymed verse," from O.Fr.
rime (fem.), related to O.Prov.
rim (masc.), earlier
*ritme, from L.
rithmus, from Gk.
rhythmos "measured motion, time, proportion" (see
rhythm).
"In MedL. rithmus was used of accentual, as opposed to quantitative, verse, and, as accentual verse was usually rhymed, the word acquired the meaning which it has in all the Rom[anic]. and Teut[onic] langs." [Weekley]
Persistence of older form is due to popular association with O.E.
rim "number," from PIE base
*re(i)- "to reason, count." The verb is first attested 1672 (of words), "to have the same end sound;" 1697 (of poets), "to make rhymes." Phrase
rhyme or reason "good sense" (chiefly used in the negative) is from 1664.
Rhyme royal (1841) is a stanza of seven 10-syllable lines rhymed a-b-a-b-b-c-c.