Latin word simplus comes from Italian scemare, Latin sem-, Latin pleo (To fill, to fulfill.)
scemare (Italian)
(intransitive) to abate (wind speed). (intransitive) to decline (in force). (intransitive) to lessen.
sem- (Latin)
pleo (Latin)
To fill, to fulfill.
scemo (Italian)
Stupid, silly Fool, idiot.
simplus (Latin)
Simple.