rhyme: [12] Etymologically, rhyme and rhythm are the same word. Both go back to medieval Latin rythmus ‘rhythm’, but whereas rhythm has reached us almost unchanged, rhyme has come via a branch line. The sort of accented verse to which the medieval Latin word was applied commonly rhymed, and so when rythmus passed into early Old French as *ritme, it carried connotations of ‘rhyming’ with it.
This later developed to rime, and when English borrowed it as rime, it still contained the notion of ‘rhythm’; but by the 13th century ‘rhyme’ was becoming its main meaning. The spelling rhyme, which emerged around 1600, represents a conscious partial return to the word’s ultimate ancestors, Latin rhythmus and Greek rhuthmós. => rhythm
rhyme (n.)
"agreement in terminal sounds," 1560s, partially restored spelling, from Middle English ryme, rime (c. 1200) "measure, meter, rhythm," later "rhymed verse" (mid-13c.), from Old French rime (fem.), related to Old Provençal rim (masc.), earlier *ritme, from Latin rithmus, from Greek rhythmos "measured motion, time, proportion" (see rhythm).
In Medieval Latin, rithmus was used for accentual, as opposed to quantitative, verse, and accentual verse usually was rhymed, hence the sense shift. Persistence of older form is due to popular association with Old English rim "number," from PIE root *re(i)- "to reason, count" (see read (v.)). Phrase rhyme or reason "good sense" (chiefly used in the negative) is from late 15c. (see reason (n.)). Rhyme scheme is attested from 1931. Rhyme royal (1841) is a stanza of seven 10-syllable lines rhymed a-b-a-b-b-c-c.
rhyme (v.)
"make verses, make rhymes," c. 1300, rimen, from Old French rimer, from rime "verse" (see rhyme (n.)). Attested 1670s (of words) in sense "to have the same end sound." Modern spelling is from 1650s, by influence of rhythm. Related: Rhymed; rhyming. The phrase rhyming slang is attested from 1859.