"good faith, fair dealing, freedom from intent to deceive," by 1838, English pluralization of bona fide, as though the Latin phrase were a noun. Sense of "guarantees of good faith" is by 1944. The opposite is mala fides "bad faith, intent to deceive."
early 15c., "one who imitates or makes a copy of," especially with intent to deceive or defraud, agent noun from counterfeit (v.).
"act or fact of feigning or making a copy of," especially with intent to deceive or defraud; verbal noun from counterfeit (v.). Earlier was counterfeiture (early 14c.).