The Collaborative International Dictionary of English v.0.48:

Mutuary \Mu"tu*a*ry\, n. [L. mutuarius mutual.See Mutuation.]
   (Law)
   One who borrows personal chattels which are to be consumed by
   him, and which he is to return or repay in kind. --Bouvier.
   [1913 Webster]

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

MUTUARY, contracts. A person who borrows personal chattels to be consumed by
him, and returned to the lender in kind; the person who receives the benefit
arising from the contract of mutuum. Story, Bailm. Sec. 47.