Fridgetair and Kelvinator

Listen up, buttercup. This joke is a pun. "Fridgetair" and "Kelvinator" sound like "frigate air" and "Kelvin ater" which sounds like "ate an," and Kelvin is a unit of temperature often associated with refrigeration. So the joke is playing on words related to refrigerators. Bet you didn't know Kelvin was a unit of temperature. That's because you live under a rock.