late 14c., "one who or that lays" (especially stones, "a mason"), agent noun from lay (v.). Passive sense of "that which is laid over a surface" first recorded 1610s, but because earliest English use was in cookery, this is perhaps from French liue "binding," used of a thickened sauce. Layer cake attested from 1881.
1832, from layer (n.). Related: Layered; layering.
layer lay·er (lā'ər)
A single thickness of a material covering a surface or forming an overlying part or segment. v. lay·ered, lay·er·ing, lay·ers
To divide or form into layers.