n. slang for a microwave (the thing in your kitchen not a really small wave pattern).

Microwaves seemed to emerge in the 80s when Americans were still fairly conscious of nuclear power, and occasionally worried about one melting down and frying us. Along comes this device that doesn't produce any heat itself but instead utilizes quasi-magical "microwaves" oooh ahhh. Similar to how magical "radiation" fries your ass when a nuclear power plant goes south.

Thus thoughts of nuclear radiation combined with magically heated food in the nuke-u-wave.