Upanishad (n.) Look up Upanishad at Dictionary.com
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 root *sed- (1) "to sit."