c. 1300, wirien, "to slay, kill or injure by biting and shaking the throat" (as a dog or wolf does), from Old English wyrgan "to strangle," from Proto-Germanic *wurgjan (source also of Middle Dutch worghen, Dutch worgen, Old High German wurgen, German würgen "to strangle," Old Norse virgill "rope"), from *wergh-, from PIE root *wer- (2) "to turn, bend."
The "strangle" sense generally was obsolete in English after c. 1600; the figurative meaning "to annoy, bother, vex" is by c. 1400. Meaning "to cause mental distress or trouble" is attested from 1822; intransitive sense of "to feel anxiety or mental trouble" is attested by 1860. Related: Worried; worrier; worrying.
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).