Merriam-Webster's Collegiate® Dictionary, 11th Edition
BELAY
I. verb (belayed; belaying)
Etymology: Middle English beleggen to beset, from Old English belecgan, from be- + lecgan to lay
Date: 1549
transitive verb
1. to secure (as a rope) by turns around a cleat, pin, or bitt, to make fast, stop ,
3. to secure (a person) at the end of a rope, to secure (a rope) to a person or object, intransitive verb to be made fast, stop , quit , to make a line fast by turns around a cleat, pin, or bitt, belayer noun
II. noun
Date: 1908
the securing of a person or a safety rope to an anchor point (as during mountain climbing), something (as a projection of rock) to which a person or rope is anchored