Meaning

verb make believe with the intent to deceive

verb hide under a false appearance

verb behave unnaturally or affectedly

originFirst attested in the beginning of the 15th century, in Middle English; inherited from Middle English dissemblen, dissimblen, dissemelen, borrowed from Old French dessambler, dissembler, disembler, itself borrowed from Latin dissimulō and modified after sembler, semblance, etc. Doublet of dissimulate, dissimilate, and dissimule. Displaced native Old English mīþan.

Etymology from Wiktionary, CC BY-SA 3.0