1580s, "enclose with walls, shut up, confine," from Middle French emmurer and directly from Medieval Latin immurare, literally "to shut up within walls," from assimilated form of in- "into, in" (from PIE root *en "in") + Latin murus "wall" (see mural). Military sense of "fortify" is from 1590s. Related: Immured; immuring; immurement.
