one of a class of speculative treatises in Sanskrit literature, 1805, from Sanskrit upa-nishad, literally "a sitting down beside." From upa "near to" (see up, adv.) + ni-shad "to sit or lie down," from ni "downward" (from PIE *ni-, see nether) + -sad "sitting," From PIE *sed- (1) "to sit" (see sedentary).