Origin: 1275–1325;Middle Englishdesmay (noun), de(s)mayen, dismayen (v.) < presumed AF alteration, by prefix change, of Old Frenchesmaier to trouble, frighten < Vulgar Latin*exmagāre to disable, deprive of strength, equivalent to ex-ex- + *magāre < Germanic*magan to be able to; see may1
c.1300, from O.Fr. *desmaier, from L. de- intensive prefix + O.Fr. esmaier "to trouble, disturb," from V.L. *exmagare "divest of power or ability," from P.Gmc. stem *mag- "power, ability" (cf. O.H.G. magen "to be powerful or able;" see may (v.)). Related: Dismayed.