You mean the flange on the axle? The part the wheel studs are on?
If so, as Scooby Doo says "Rut Row". If the flange is wobbling, in/out as it rotates you somehow bent it. If it's wobbling up and down, you bent the axle shaft.
97 Sahara, 74 Renegade, 72 CJ5, 55 Willy's (the Beast) Boss 302, 6:34 gearing, Bose 901 speakers.
God I miss that Jeep. Forgot the kinda Jeep, 80 SX4.