also diss, slang, by 1980, shortening of disrespect or dismiss, originally in U.S. Black English, popularized by hip hop. Related: Dissed; dissing. Earlier it was short for disconnected in the telephone sense and used figuratively in slang to mean "weak in the head" (1925).
Roman underworld god, from Latin Dis, contracted from dives "rich," which is related to divus "divine, god," hence "favored by god." Cf. Pluto and Old Church Slavonic bogatu "rich," from bogu "god."
(also diss; on may be added) To show disrespect; insult by slighting; CAP ON someone: The boys on the bus were dissing that girl/ Yet ''dissin','' showing real or apparent disrespect, is cited as the motive in an amazing number of murders/ I'm tired of John dissin' on her all the time (1980s+ Black teenagers)