mid-15c., "a heap; the volume or bulk of something," earlier "ship's cargo" (mid-14c.), from a Scandinavian source akin to Old Norse bulki "a heap; ship's cargo," from Proto-Germanic *bul-, from PIE root *bhel- (2) "to blow, swell."
Meaning extended by early confusion with obsolete bouk "belly" (from Old English buc "body, belly," from Proto-Germanic *bukaz; see bucket), which led to sense of "size, volume, magnitude of material substance," attested from mid-15c. In bulk 1670s, "loaded loose." Meaning "the greater part" (of anything) is by 1711.
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).
<a href="https://www.etymonline.com/word/bulky">Etymology of bulky by etymonline</a>
Harper, D. (n.d.). Etymology of bulky. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/bulky