hog (n.)youdaoicibaDictYouDict[hog 词源字典]
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.[hog etymology, hog origin, 英语词源]
road (n.)youdaoicibaDictYouDict
Old English rad "riding expedition, journey, hostile incursion," from Proto-Germanic *raido (cognates: Old Frisian red "ride," Old Saxon reda, Middle Dutch rede, Old High German reita "foray, raid"), from PIE *reidh- "to ride" (see ride (v.)). Also related to raid (n.). In Middle English, "a riding, a journey;" sense of "open way for traveling between two places" is first recorded 1590s. Meaning "narrow stretch of sheltered water" is from early 14c. (as in Hampton Roads in Virginia).

Modern spelling established 18c. In 19c. U.S. use, often meaning "railroad." On the road "travelling" is from 1640s. Road test (n.) is from 1906; as a verb from 1937. Road hog is attested from 1886; road rage is from 1988. Road map is from 1786; road trip is by 1950, originally of baseball teams. Old English had radwerig "weary of travelling."