Word Origin and History for s. roger david casement
1430, probably aphetic of O.Fr. dial. enchassement "window frame," from en- "in," prefix forming verbs, + casse "case, frame" (see case (2)) + -ment. Or possibly from Anglo-L. cassementum, from casse. The Irish surname is originally Mc Casmonde (attested from 1429), from Mac Asmundr, from Ir. mac "son of" + O.N. Asmundr "god protector."