Chambers's Twentieth Century Dictionary…
“ Mortise, mor′tis, n. a cavity cut into a piece of timber to receive the tenon, a projection on another piece made to fit it: stability, power of adhesion—also Mor′tice.—v.t. to cut a mortise in: to join by a mortise and tenon. [Fr. mortaise; ety. unknown.] Mortmain, mort′mān, n. the transfer of property to a corporation, which is said to be a dead hand, or one that can never part with it again.—Statutes of mortmain, acts of parliament restricting or forbidding the giving of property to religious houses. [Fr. mort, dead, main—L. manus, the hand.] ”
