What is this kind of crypto called?

I once read of a python library for creating a certain type of
cryptography. I've forgotten the keyword for this kind of crypto and
so I can't find it!

What I'm talking about: You encrypt a file, and generate three keys,
and give a key to each of three people. No single key can open the
file. It requires *any two* of the three keys to open it.

What's the term for this? Not "federated?" Is "escrow" in there
somewhere? Can one of you crypto-spook types help me name what I'm
looking for?
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