faux naïf

 
Pronunciation: /ˌfəʊ nʌɪˈiːf, fo naif/

adjective

  • artificially or affectedly simple or naive: faux-naif pastoralism

noun

  • a person who pretends to be ingenuous: the speaker in these stories sounds authentically ten years old, never lapsing into the coyness of the faux naif

Origin:

from French faux 'false' + naïf 'naive'