This question comes from a comment to another question.

Craster must have somehow known that by putting out his baby boys, he would be protected by the White Walkers.

And the White Walkers must have learned Craster's Keep was a source of fresh recruits.

But how did that arrangement start? Is there anything in the books that mentions how?

This question comes from a comment to another question.

Craster must have somehow known that by putting out his baby boys, he would be protected by the White Walkers.

And the White Walkers must have learned Craster's Keep was a source of fresh recruits.

But how did that arrangement start? Is there anything in the books that mentions how?