mantra (n.)youdaoicibaDictYouDict
1808, "that part of the Vedas which contains hymns," from Sanskrit mantra-s "sacred message or text, charm, spell, counsel," literally "instrument of thought," related to manyate "thinks," from PIE root *men- "to think" (see mind (n.)). Sense of "special word used for meditation" is first recorded in English 1956.
tantra (n.)youdaoicibaDictYouDict
type of Hindu religious book, 1799, from Sanskrit tantram, literally "loom, warp," hence, figuratively, "groundwork, system, doctrine," from tan "to stretch, extend," from PIE root *ten- "to stretch, extend" (see tenet).