The Collaborative International Dictionary of English v.0.48:

Timorous \Tim"or*ous\, a. [LL. timorosus, from L. timor fear;
   akin to timere to fear. See Timid.]
   1. Fearful of danger; timid; deficient in courage. --Shak.
      [1913 Webster]

   2. Indicating, or caused by, fear; as, timorous doubts. "The
      timorous apostasy of chuchmen." --Milman.
      [1913 Webster] -- Tim"or*ous*ly, adv. --
      Tim"or*ous*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

timorously
    adv 1: in a timorous and trepid manner [syn: timorously,
           trepidly]