c.1300, verbal noun from ride, v.. Meaning "teasing, annoying" is from 1927. Riding-hood, worn by women when riding or exposed to weather, is from mid-15c.

one of the three districts into which Yorkshire was divided, late 13c., from late Old English *þriðing, a relic of Viking rule, from Old Norse ðriðjungr "third part," from ðriði "third" (see third). The initial consonant merged with final consonant of preceding north, west, or east.