horribly (adv.)

c. 1300, "dreadful, terrible," from Old French horrible, orrible (12c.) "horrible, repugnant, terrifying," from Latin horribilis "terrible, fearful, dreadful" (source also of Spanish horrible, Portuguese horrivel, Italian orribile), from horrere "be terrified, bristle with fear, shudder" (see horror). Used as a mere intensifier from mid-15c.

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.