Word Origin & History
c.1175 (implied in hogaster), "swine reared for slaughter" (usually about a year old), also used by stockmen for "young sheep" (c.1350) 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 O.E., but it may have existed.
Possibility of Celtic origin is regarded by OED as "improbable." Fig. sense of "gluttonous person" is first recorded 1436. Meaning "Harley-Davidson motorcycle" is attested from 1967. The verb meaning "to appropriate greedily" is U.S. slang from 1884 (first attested in "Huck Finn"). The verb hog-tie "bind hands and feet" is first recorded 1894. Hog in armor "awkward or clumsy person in ill-fitting attire" is from 1660. 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 Eng. 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.