What does AT-AT stand for?

What does AT-AT stand for?
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There are two kinds of people — Star Wars fans who bicker over how to pronounce vehicle names and those who bicker with those fans about bickering too often over Star Wars.

If that sentence actually made sense to you, this question should be a breeze.

AT-ATs quickly earned a place in our hearts when they debuted in 1980's The Empire Strikes Back. They look, really, really cool — and they seem like they could do some damage... as long as they don't have to go up against a lone Jedi or a tow cable.

What do the letters in this Imperial acronym stand for?

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