magniloquent (adj.)

1650s, a back-formation from magniloquence, or else from Latin magniloquentia "lofty style of language," from magniloquus "pompous in talk, vaunting, boastful," from combining form of magnus "great" (from PIE root *meg- "great") + -loquus "speaking," from loqui "to speak" (from PIE root *tolkw- "to speak").