Other forms: belaying, belays, belayed
To belay is to hold the rope safe for a climber above you. Belay the leader, on belay, belay device.
The belayer's job is to take in slack and to lock the rope if the climber falls, so the two are a single system and the calls between them are fixed words for that reason. At sea, belay means to make a rope fast, and belay that means cancel that order.
1verbbelayTo hold the rope safe for a climber above you.
“Hold the rope tight and belay me while I climb up to the ledge.”
belay is a securing.
be-LAY → you LAY the rope and hold it
You lay the rope across your body and hold it while the other one climbs.
hooks ontolay
Old English belecgan meant to lay about or cover. The nautical sense of making a rope fast came first.
Proto-West Germanic
*bilaggjan
Old English
beleċġan — to cover, invest, surround, afflict, attribute to, charge with, accuse
Middle English
beleggen
English, today
belay
From Middle English beleggen, bileggen, from Old English beleċġan (“to cover, invest, surround, afflict, attribute to, charge with, accuse”), From Proto-West Germanic bilaggjan, equivalent to be- + lay. Cognate with Dutch beleggen (“to cover, overlay, belay”), German belegen (“to cover, occupy, belay”), Swedish belägga (“to pave”).
Etymology from Wiktionary, CC BY-SA