harshly (adv.)

originally of texture, "hairy," 1530s, probably from Middle English harske "rough, coarse, sour" (c. 1300), a northern word of Scandinavian origin (compare Danish and Norwegian harsk "rancid, rank"), related to Middle Low German harsch "rough, raw," German harst "a rake;" perhaps from PIE root *kars- "to scrape, scratch, rub, card" (source also of Lithuanian karšiu, karšti "to comb," Old Church Slavonic krasta, Russian korosta "scab," Latin carduus "thistle," Sanskrit kasati "rubs, scratches"). Meaning "offensive to feelings" is from 1570s; that of "disagreeable, rude" from 1610s.

common adverbial suffix, forming from adjectives adverbs signifying "in a manner denoted by" the adjective, Middle English, from Old English -lice, from Proto-Germanic *-liko- (cognates: Old Frisian -like, Old Saxon -liko, Dutch -lijk, Old High German -licho, German -lich, Old Norse -liga, Gothic -leiko); see -ly (1). Cognate with lich, and identical with like (adj.).

Weekley notes as "curious" that Germanic uses a word essentially meaning "body" for the adverbial formation, while Romanic uses one meaning "mind" (as in French constamment from Latin constanti mente). The modern English form emerged in late Middle English, probably from influence of Old Norse -liga.