Some politicians change the boundaries of their voting districts in order to benefit themselves or their political party. To manipulate the boundaries like this — often viewed as unfair — is to gerrymander.
The verb gerrymander first appeared in 1812 when Massachusetts governor Elbridge Gerry redrew district boundaries, hoping it would help his party in an upcoming senate election. Then somebody noticed that the new district looked like a salamander, so they combined Gerry and -mander to create the new word gerrymander. And then a newspaper printed a cartoon with a giant salamander making fun of Gerry, which is what happens to politicians who don’t behave.