Protected the king, in a way

Usage examples of castled.

Oh, he knew the rules, and the rudiments, and even some of the refinements, but he had no grasp whatsoever of such instruments as the gambit, the knight fork, or the defrocked bishop, and while he was all too eager to demonstrate he knew how to castle, he castled kingside when he should have castled queenside, and he castled either side when he did not need to castle at all.

There are pins and counter-pins, attacks and latent and discovered attacks, and White's threat to break up Black's castled position.