Ledasdottir offers: put one fist into the joint of your elbow and raise the other fist up, with knuckles facing out

This is very similar to the ASL gesture meaning "Good Morning", particularly if you add the opening of the hand at the end of the former gesture.

Fiorello LaGuardia grew up speaking English, Italian and Yiddish. It has been reported that you could tell from silent movies (probably non-voice over newsreels) of him giving speeches what language he was speaking by the hand gestures he used.