late 12c. (implied in hogaster), "swine reared for slaughter" (usually about a year old), also used by stockmen for "young sheep" (mid-14c.) and for "horse older than one year," suggesting the original sense had something to do with an age, not a type of animal. Not evidenced in Old English, but it may have existed. Possibility of British Celtic origin [Watkins, etc.] is regarded by OED as "improbable." Figurative sense of "gluttonous person" is first recorded early 15c. Meaning "Harley-Davidson motorcycle" is attested from 1967.To go hog wild is from 1904. Hog in armor "awkward or clumsy person in ill-fitting attire" is from 1650s. Phrase to go the whole hog (1828) is sometimes said to be from the butcher shop option of buying the whole slaughtered animal (at a discount) rather than just the choice bits. But it is perhaps rather from the story (recorded in English from 1779) of Muslim sophists, forbidden by the Quran from eating a certain unnamed part of the hog, who debated which part was intended and managed to exempt the whole of it from the prohibition. Road hog is attested from 1886.

"to appropriate greedily," U.S. slang, 1884 (first attested in "Huck Finn"), from hog, n.. Related: Hogged; hogging.