Comment: The "T" word here is "Taquiyya".  The other word is "kitman".

"In Shi'a Islam, taqiya is a form of religious lie, or a legal dispensation whereby a believing individual can deny his faith or commit otherwise illegal or blasphemous acts,"


"A related concept is known as kitman "concealment; dissimulation by omission".

Both are permitted against enemies.  

Yarden Mariuma writes: "Taqiyya is an Islamic juridical term whose shifting meaning relates to when a Muslim is allowed, under Sharia law, to lie. A concept whose meaning has varied significantly among Islamic sects, scholars, countries, and political regimes,