Old English utera, uterra, "outer, exterior, external," from Proto-Germanic *utizon (source also of Old Norse utar, Old Frisian uttra, Middle Dutch utere, Dutch uiter-, Old High German uzar, German äußer "outer"), comparative adjective from ut (see out (adv.)). Meaning "complete, total" (i.e. "going to the utmost point") is from early 15c.
"speak, say," c. 1400, in part from Middle Dutch uteren or Middle Low German utern "to turn out, show, speak," from uter "outer," comparative adjective from ut "out" (see utter (adj.)); in part from Middle English verb outen "to disclose," from Old English utan "to put out," from ut (see out (v.)). Compare German äussern "to utter, express," from aus "out;" and colloquial phrase out with it "speak up!" Formerly also used as a commercial verb (as release is now). Related: Uttered; uttering.