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).

word-forming element meaning "the body," Modern Latin, from Greek sōma "the body" (see somato-).

Old English sum "some, a, a certain one, something, a certain quantity; a certain number;" with numerals "out of" (as in sum feowra "one of four"); from Proto-Germanic *sumaz (source also of Old Saxon, Old Frisian, Old High German sum, Old Norse sumr, Gothic sums), from PIE *smm-o-, suffixed form of root *sem- (1) "one; as one, together with." For substitution of -o- for -u-, see come.

The word has had greater currency in English than in the other Teutonic languages, in some of which it is now restricted to dialect use, or represented only by derivatives or compounds .... [OED]

As a pronoun from c. 1100; as an adverb from late 13c. Meaning "remarkable" is attested from 1808, American English colloquial. A possessive form is attested from 1560s, but always was rare. Many combination forms (somewhat, sometime, somewhere) were in Middle English but often written as two words till 17-19c. Somewhen is rare and since 19c. used almost exclusively in combination with the more common compounds; somewho "someone" is attested from late 14c. but did not endure. Scott (1816) has somegate "somewhere, in some way, somehow," and somekins "some kind of a" is recorded from c. 1200. Get some "have sexual intercourse" is attested 1899 in a quote attributed to Abe Lincoln from c. 1840.