How did the Bazooka gun get its name?

Kwll will probably jump on this, as the bazooka is not technically a "gun." Weapon, yes; gun, no.

I believe it was named after a popular children's toy.

According to this, it was a musical instrument. Fedex probably played one as a youngster, thinking it was a toy.

http://www.wikipedia.org/wiki/Bazooka

My reference agrees with SR in that it resembled the musical instrument of comedian Bob Burns.

Yes, XFED, not a gun at all. Actually is rocket launcher that fired a shaped charged anti tank warhead known as a HEAT (High Explosive Anti-Tank) rounds that would fire a "heat jet" that melts the metal it comes into contact with. This principle is still in use today but mostly in "missiles". Tanks firing against tanks tend to use kinetic energy weapons. Good picture and description at the link.
http://www.geocities.com/Augusta/8172/panzerfaust13.htm

IT was developed during ww11 was named after the humorous musical instrument that radio entertainer Bob Burns had fashioned from two gas pipes and a funnel!