also 'neath, 1787, poetic shortening of beneath (q.v.).
Entries linking to neath
beneath adv., prep.
Middle English binethe, from Old English beneoðan "under, below, in a lower place, further down than," in late Old English "lower in rank, degree, excellence, etc.," from be- "by" + neoðan "below, down, from below," from Proto-Germanic *niþar "lower, farther down, down" (see nether).
The meaning "unworthy of" is attested from 1849 (purists prefer below in this sense). "The be- gave or emphasized the notion of 'where,' excluding that of 'whence' pertaining to the simple niðan" [OED].