I’ve never heard this word. I’ve never heard anyone use it; I’ve never read it. What’s more, I’ve never heard my MOTHER use this word (and, of course, Mother knows everything). It’s new to me.
It made me think of Jamie Frasier, in Diana Gabaldon’s Outlander series, but on reflection, while Jamie was miserable in prison, I think he had enough purpose in seeing to the care of his men that you couldn’t say he was caitiff. Now, the MEN may have been caitiff.
You learn something every day.
(N.B. When I ran Spell Check, it made no comment about “caitiff.”)