apostasy

luopumus, apostaasi The renunciation of a belief or set of beliefs.
1871, James Anthony Froude, History of England from the Fall of Wolsey to the Death of Elizabeth, page 394

The King of Navarre suddenly abandoned his party and went over to the Catholics. The explanation of his apostasy was as simple as it was base: Navarre had no confidence in the success of his cause, and he cared little in his heart for anything but women and vanity.

What had he said, what had he done, after all, to give them the right to fasten on him the charge of apostasy? He had always been a free critic of everything, and it was natural that, on certain occasions, in the little parlour in Lisson Grove, he should have spoken in accordance with that freedom; but it was only with the Princess that he had permitted himself really to rail at the democracy and given the full measure of his scepticism.