Yours, Etc.: Origins and Uses of 8 Sign-Offs
late 13c., from Old French reverence "respect, awe," from Latin reverentia "awe, respect," from revereri "to stand in awe of, respect, honor, fear, be afraid of; revere," from re-, intensive prefix (see re-), + vereri "stand in awe of, fear," from PIE *wer- "to be or become aware of, perceive, watch out for" (cf. Old English wær "aware, cautious;" see wary).
late 14c., "treat with respect, honor; venerate, pay pious homage to; esteem, value; bow to (someone); do honor to," from reverence (n.). Related: Reverenced; reverencing.