billowy (adj.)

"a great wave or surge of the sea," 1550s, perhaps older in dialectal use (but not recorded in Middle English), from Old Norse bylgja "a wave, a billow," from Proto-Germanic *bulgjan (source also of Swedish bölja, Danish bölge "a billow," Middle High German bulge "a billow; a bag"), from PIE *bhelgh- "to swell," extended form of root *bhel- (2) "to blow, swell."

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). Adjectives such as hugy, vasty are artificial words that exist for the sake of poetical metrics.