late 14c., basken "to wallow" (especially in warm water or blood, of unknown etymology. The Middle English Compendium rejects the derivation from Old Norse baðask "to bathe oneself" (with loss of middle syllable), reflexive of baða "bathe" (see bathe) + Proto-Germanic *-sik "one's self" (source also of German sich; see -sk).

The meaning "soak up a flood of warmth" is apparently due to Shakespeare's use of the word in reference to sunshine in "As You Like It" (1600). Related: Basked; basking.

1742, present-participle adjective from bask (v.). The basking shark (1769) is named for frequently being seen basking on the surface of the sea.

reflexive suffix in words of Danish origin (such as bask, literally "to bathe oneself"), contracted from Old Norse sik, reflexive pronoun corresponding to Gothic sik, Old High German sih, German sich "himself, herself, itself," from PIE root *s(w)e- (source of Latin se "himself;" see idiom).

1690s, "to bask in the sun," from Latin apricatus, past participle of apricari "to bask in the sun," from apricus "exposed" (to the sun; the antonym of opacus "shady"). This is perhaps contracted from *apericus, a derivative of aperire "to open" (see overt). The transitive sense is recorded from 1851. Related: Aprication.

"to bask in the warmth" of something, early 13c., a northern and Scottish word of unknown origin; perhaps ultimately connected to bake (v.).

"a blow," c. 1300, of uncertain origin, older than the verb, possibly related to Middle Dutch boke, Middle High German buc, and Danish bask, all meaning "a blow;" perhaps imitative or perhaps from some sense of box (n.1) or (v.2).