According to a variety of sources, the word "TASER" was coined as an acronym for "Thomas A. Swift's Electric Rifle." Apparently the Taser's inventor was a fan of the Tom Swift books, and named it after Tom Swift and His Electric Rifle. (Wikipedia says that the inventor made up the "A" middle initial.)
I find that hard to believe, but several independent sources mention it, and I can't find any that contradict it.