An etiquette question-mostly for Jewish people.

[BertrandRussell]

Many years ago when my father died someone said to me “May his memory be a blessing” and I adopted it in various forms as my go-to condolence phrase. I discovered recently that it’s a phrase from Jewish ritual? Culture? Is it OK for me to use it still? I have no Jewish links at all.

I don't see why you shouldn't. Lots of phrases leak from one religion or another to popular culture, nobody owns them really.
"yehi zichra baruch"

Yes, it’s absolutely fine to say. It isn’t a strictly religious phrase. It’s more of a cultural one. And certainly I say this to non-Jewish friends who probably have no idea it has an Jewish roots. I think it’s a really lovely and comforting thing to say to someone.

Thank you very much- I would have hated to give it up. I dislike all the other stock phrases.