1580s, from toil (v.) + -some (1). An earlier word was toilous (early 15c.). The opposite, toilless (c. 1600) is much less common.
Entries linking to toilsome
toil v.
early 14c., toilen, "pull at, tug," from Anglo-French toiller, Old French toellier "pull or drag about" (see toil (n.1)). Intransitive meaning "struggle, work hard, labor for considerable time" is from late 14c., perhaps by influence of till (v.). Related: Toiled; toiling.
-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).