layer (n.) Look up layer at Dictionary.com
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.
layer (v.) Look up layer at Dictionary.com
1832, from layer (n.). Related: Layered; layering.