The Collaborative International Dictionary of English v.0.48:

Nathless \Nath"less\, adv. [OE. natheles, na the les, not the
   less, AS. n[=a] never. See Na, The, conj., and cf.
   Nevertheless.]
   Nevertheless. [Archaic] --Chaucer. --Milton. --E. Arnold.
   [1913 Webster]