The Collaborative International Dictionary of English v.0.48:

Devisor \De*vis"or\, n. (Law)
   One who devises, or gives real estate by will; a testator; --
   correlative to devisee.
   [1913 Webster]

WordNet (r) 3.0 (2006):

devisor
    n 1: someone who devises real property in a will

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

DEVISOR. A testator; one, who devises his real estate.
     2. As a general rule all persons who. may sell an estate may devise it.
The disabilities of devisors may be classed, in three divisions. 1. Infancy.
In some of the United States this disability is partially removed; in
Illinois, Maryland, Mississippi and Ohio, an unmarried woman at the age of
eighteen years may devise. 2. Coverture. In general, a married woman cannot
devise; but in. Connecticut and Ohio she may devise her lands; and in
Illinois, her separate estate. In Louisiana, she may devise without the
consent of her husband. Code, art. 132. 3. Idiocy and non sane memory. It is
evident that a person non compos can make no devise, because he has no will.
     3. The removal of the disability which existed at the time of the
devise does, not, of itself, render it valid. For example, when the husband
dies, and the wife becomes a feme sole; when one non compos is restored to
his sense; and when an infant becomes of age; these several acts do not make
a will good, which at its making was void. 11 Mod. 123, 157; 2 Vern. 475;
Comb, 84; 4 Rawle, R. 3.36. Vide. Testament or ill.