The Collaborative International Dictionary of English v.0.48:

Bailor \Bail`or"\, n. (Law)
   One who delivers goods or money to another in trust.
   [1913 Webster]

WordNet (r) 3.0 (2006):

bailor
    n 1: the person who delivers personal property (goods or money)
         in trust to the bailee in a bailment

Bouvier's Law Dictionary, Revised 6th Ed (1856):

BAILOR, contracts. He who bails a thing to another.
     2. The bailor must act with good faith towards the bailee; Story's
Bailm. Sec. 74, 76, 77; permit him to enjoy the thing bailed according to
contract; and, in some bailments, as hiring, warrant the title and
possession of the thing hired, and probably, to keep it in suitable order
and repair for the purpose of the bailment. Id. Sec. Vide Inst. lib. 3, tit.
25.