1550s, "of or pertaining to comedy," from comic (or Latin comicus) + -al (1). Meaning "funny, exciting mirth" is from 1680s. Also sometimes in 17c. "befitting comedy, low, ignoble." Related: Comicality; comicalness.
late 14c., "of comedy in the classical sense, pertaining to comedy as distinct from tragedy," from Latin comicus "of comedy, represented in comedy, in comic style," from Greek komikos "of or pertaining to comedy," from komos (see comedy). Meaning "intentionally funny, raising mirth" is first recorded 1791, and comedic (1630s) has since picked up the older sense of the word.
Speaking of the masters of the comedic spirit (if I call it, as he does, the Comic Spirit, this darkened generation will suppose me to refer to the animal spirits of tomfools and merryandrews) .... [G.B. Shaw, 1897]
Something that is comic has comedy as its aim or origin; something is comical if the effect is comedy, whether intended or not. Comic relief is attested from 1817.