The Collaborative International Dictionary of English v.0.48:

Swarthiness \Swarth"i*ness\, n.
   The quality or state of being swarthy; a dusky or dark
   complexion; tawniness.
   [1913 Webster]

WordNet (r) 3.0 (2006):

swarthiness
    n 1: a swarthy complexion [syn: darkness, duskiness,
         swarthiness]