-rel

1630s, "Any rhyming verse in which the meter is forced into metronomic regularity by the stressing of normally unstressed syllables and in which rhyme is forced or banal" [Miller Williams, "Patterns of Poetry"]. Earlier as an adjective (rim doggerel, late 14c.), an epithet applied to loose, irregular verse in burlesque poetry.

Probably from pejorative suffix -rel + dog (n.), but the sense connection is not obvious. Perhaps it was applied to bad poetry with a suggestion of puppyish clumsiness, or being fit only for dogs, or from the "mean, contemptible" associations of dog in Middle English. Attested as a surname from late 13c., but the sense is not evident. Related: Doggerelist.

mid-15c., "individual or breed of dog resulting from repeated crossings or mixture of several different varieties," from obsolete mong "mixture," from Old English gemong "mingling" (base of among), from Proto-Germanic *mangjan "to knead together" (source of mingle), from a nasalized form of PIE root *mag- "to knead, fashion, fit." With pejorative suffix -rel.

The distinction between a mongrel and a hybrid (a cross between two different breeds) is not always observed. Meaning "person not of pure race" is attested from 1540s. As an adjective, "of a mixed or impure breed," from 1570s.