This is an interesting word. I have come across it in a non-yiddish context a couple of times. When I look it up in Merriam Webster online, because I recognize the Yiddish word, I am told :
Definition of fremd
1 now chiefly Scottish : foreign, unfamiliar
2 now chiefly Scottish : not belonging to one's own family or household : unrelated
— fremdly adverb
— fremdness noun, plural -es