not to mention, in addition to; without mentioning: We were served a sumptuous entree, not to mention the other courses.
Origin: 1250–1300; < Latin mentiōn- (stem of mentiō) a calling to mind, a touching upon (see mental1, -ion); replacing Middle English mencioun < Anglo-French < Latin, as above
c.1300, from O.Fr. mencion "call to mind," from L. mentionem (nom. mentio) "a calling to mind, a speaking of, mention," from root of Old L. minisci "to think," related to mens (gen. mentis) "mind," from PIE base *men- "think" (see mental). The verb is first attested 1520s.