[angry dispute] mid-14c., querele, "dispute, altercation," also "ground for complaint," from Old French querele "matter, concern, business; dispute, controversy" (Modern French querelle) and directly from Latin querella "complaint, accusation; lamentation," from queri "to complain, lament," from Proto-Italic *kwese-, of uncertain etymology, perhaps, via the notion of "to sigh," from a PIE root *kues- "to hiss" (source also of Sanskrit svasiti "to hiss, snort"), which is not very compelling, but no better etymology has been offered.
In Middle English also of armed combat. Old English had sacan. Sense of "angry contention between persons" is from 1570s.
A quarrel is a matter of ill feeling and hard words in view of supposed wrong : it stops just short of blows; any use beyond this is now figurative. [Century Dictionary, 1897]
word-forming element used in making adjectives from nouns or adjectives (and sometimes verbs) and meaning "tending to; causing; to a considerable degree," from Old English -sum, identical with some, from PIE root *sem- (1) "one; as one, together with." Cognate with Old Frisian -sum, German -sam, Old Norse -samr; also related to same. "It usually indicates the possession of a considerable degree of the quality named: as mettlesome, full of mettle or spirit; gladsome, very glad or joyous" [Century Dictionary]. For the -some used with numbers (twosome, foursome, etc.), see -some (2).