What does Boxing Day have to do with boxing?
1921 (n.), 1923 (v.), from hitch, from the notion of hitching a sled to a moving vehicle (a sense first recorded 1880) + hike. Related: Hitchhiked; hitchhiking. Hitchhiker attested from 1927.
To get free rides by standing beside a road and signaling drivers; hitch, thumb (1923+)