nethermost

from WordNet (r) 3.0 (2006)

nethermost
    adj 1: farthest down; "bottommost shelf" [syn: {bottommost},
           {lowermost}, {nethermost}]

from The Collaborative International Dictionary of English v.0.48

Nethermost \Neth"er*most`\ (n[e^][th]"[~e]r*m[=o]st`), a. [AS.
   ni[eth]emest. See {Nether}, and cf. {Aftermost}.]
   Lowest; as, the nethermost abyss. --Milton.
   [1913 Webster]