とも in どこの馬の骨とも知らない

Question

どこの馬の骨とも知らない男

I am aware that「どこの馬の骨とも知らない」is an idiomatic phrase meaning "unknown" but what does it literally mean? "Not knowing whatever horse's bone"? What is the role of と before も? Is も connected to どこ?

Answer 1

知る actually can take と as a particle. For the difference between ～を知る and ～と知る, see this answer:

How do you use 〜と知る?

I don't fully agree with the answer though. I feel like the differentiation seems more complicated than presented in that answer, but the suggested test—try swapping in 分かる—is a good rule of thumb to go by. And I believe it's also common to hear 「どこの馬の骨とも分からないやつ」

This も just means "even", as in 「猿も木から落ちる」 ("Even monkeys fall from trees")

どこの馬の骨とも知らない男
a man whom we know nothing about, a total stranger, someone whose basic background we don't even know