mid-15c., "weary," also "causing weariness," from weary + -some (1).
Entries linking to wearisome
weary adj.
Old English werig "tired, exhausted; miserable, sad," related to worian "to wander, totter," from Proto-Germanic *worigaz (source also of Old Saxon worig "weary," Old High German wuorag "intoxicated"), of unknown origin.
-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).