agarrar llave

A wrestling/grappling term for applying a submission hold or lock on an opponent — used in lucha libre, judo, and jiu-jitsu alike: le agarró llave al brazo. Llave here means 'hold/lock,' not a literal key; outside combat sports, the phrase doesn't carry a separate meaning.

• El luchador le agarró llave y no lo soltó. — The wrestler locked him in a hold and wouldn't let go.
• En judo, agarrar llave al brazo es una técnica común. — In judo, applying an armlock is a common technique.
• Casi se lastima cuando le agarraron llave mal. — He almost got hurt when they applied the hold badly.

Taking llave literally as 'key' — in this fixed sports phrase it means a grappling hold or lock, a completely different, unrelated sense of the word.