adventuresome adj.

c. 1200, aventure, auenture "that which happens by chance, fortune, luck," from Old French aventure (11c.) "chance, accident, occurrence, event, happening," from Latin adventura (res) "(a thing) about to happen," from fem. of adventurus, future participle of advenire "to come to, reach, arrive at." This is from ad "to" (see ad-) + venire "to come" (from a suffixed form of PIE root *gwa- "to go, come").

The meaning developed through "risk; danger" (a trial of one's chances), c. 1300, and "perilous undertaking" (late 14c.) to "novel or exciting incident, remarkable occurrence in one's life" (1560s).

Earlier it also meant "a wonder, a miracle; accounts of marvelous things" (13c.). The -d- was restored in English 15c.-16c.; in French the attempt to restore it at about the same time was rejected. Venture is a 15c. variant. German Abenteuer is a borrowing of the French word, apparently deformed whimsically by influence of Abend "evening."

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).