Emily Dickinson Lexicon

MOR'TISE, n. [mor'tis; Fr. mortaise; Arm. mortez; Sp. mortaja; Ir. mortis. The Armoric mortez signifies both a mortar and a mortise, and the Spanish mortaja signifies a mortise and a winding sheet or shroud. In the latter sense the Portuguese use mortalha, from mortal. These alliances indicate that these words are all from the root of mors, death, which may be from beating or throwing down.]

A cut or hollow place made in timber by the augur and chisel, to receive the tenon of another piece of timber.