Old English dyppan "immerse, baptize by immersion," from Proto-Germanic *duppjan (cognates: Old Norse deypa "to dip," Danish døbe "to baptize," Old Frisian depa, Dutch dopen, German taufen, Gothic daupjan "to baptize"), related to Old English diepan "immerse, dip," and perhaps ultimately to deep. As a noun, from 1590s. Sense of "downward slope" is 1708. Meaning "sweet sauce for pudding, etc." first recorded 1825.

"stupid person, eccentric person," 1920s slang, perhaps a back-formation from dippy. "Dipshit is an emphatic form of dip (2); dipstick may be a euphemism or may reflect putative dipstick 'penis' " [DAS].