"herbaceous plant of the genus Urtica, armed with stinging hairs" (also used of other plants of the genus and of nettle-like plants, generally with a qualifying word), Middle English netle, from Old English netele, from Proto-Germanic *natilon (source also of Old Saxon netila, Middle Dutch netele, Dutch netel, German Nessel, Danish nædlæ "nettle"), diminutive of *nato-, of unknown origin, perhaps from PIE root *ned- "to bind, tie." "[N]ettles or plants of closely related genera such as hemp were used as a source of fiber" [Watkins].
-some 1
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]. It is also, disguised, the ending in buxom. For the -some used with numbers (twosome, foursome, etc.), see -some (2).