"overgrown, unwieldy," especially from excessive eating and drinking, 1660s, past-participle adjective from bloat (v.). The figurative sense "puffed up" with pride, wealth, etc., is by 1711.
Entries linking to bloated
bloat v.
1660s, "to cause to swell" (earlier, in reference to cured fish, "to cause to be soft," 1610s), from now obsolete bloat (adj.), attested from c. 1300 as "soft, flabby, flexible, pliable," but by 17c. meaning "puffed up, swollen." It is perhaps from a Scandinavian source akin to Old Norse blautr "soaked, soft from being cooked in liquid" (compare Swedish blöt fisk "soaked fish"), possibly from Proto-Germanic *blaut-, from PIE *bhleu- "to swell, well up," extended form of root *bhel- (2) "to blow, swell."
It was influenced by or combined with Old English blawan "blow, puff." The figurative use is by 1711. The intransitive meaning "to swell, to become swollen" is from 1735. Related: Bloated; bloating.