why do they call the rooks a pig?

As reported by others, Janowski referred to pigs on the seventh as blind swine for the reason noted here.

Alternately, they are blind because they can find plenty of checks but not checkmate.

it is because......... they eat pawns

Pigs on the seventh rank can 'oink' check, but not deliver checkmate.

Those are blind pigs.

i wonder if pink floyd was thinking about chess when they sang about pigs on the wing.

Yep, i'm certain that is exactly what they were contemplating. Snout full of something.

pawns?

I'm sure there's a political explanation too. Der schwein, etc LOL

The Wall also begins with WWII and what it meant to Waters and his generation to grow up without the fathers who were killed in the war.

When rooks are on the second or seventh rank, they are called pigs because the pawns on either of those ranks are helpless and most likely are going to be captured by the opposing rook.