"make a short, sharp, happy sound like a bird," mid-15c. (implied in chirping), echoic, or else a variant of Middle English chirken "to twitter" (late 14c.), from Old English cearcian "to creak, gnash." Related: Chirped. As a noun, attested from 1802.
adjective suffix, "full of or characterized by," from Old English -ig, from Proto-Germanic *-iga- (source also of Dutch, Danish, German -ig, Gothic -egs), from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Originally added to nouns in Old English; used from 13c. with verbs, and by 15c. even with other adjectives (for example crispy).
Others are reading
Definitions of chirpy
(birds or insects) characterized by or tending to chirp;