layerlayer

The story

Appears at first glance to be from Middle English leyer, leyare (‘a layer of stones or bricks’), equivalent to lay + -er. For the pronunciation compare prayer. However, this word layer (referring to a thickness of a material covering a surface) has also been argued to be from a respelling of an obsolete sense of the word lair that was once used by farmers, which had to do with soil. The connecting sense between the usual meaning of lair and the specialised farming meaning was: an area where cows typically rest, the ground being fertilised by their waste.

Full etymology on Wiktionary