1560s, "to smile in an affected and silly way," perhaps from a Scandinavian source (such as dialectal Danish semper "affected, coy, prudish") or Middle Dutch zimperlijk "affected, coy, prim," of unknown origin. Related: Simpered; simpering. As a noun, 1590s, from the verb.
simon-pure
simony
simoom
simp
simpatico
simper
simpering
simple
simple-minded
simpleness
simpleton