[exch]

They do in my (marginal) experience. I have found it to be a very common idiom to keep word definitions in these languages as short as possible. Probably for this very reason.

You define new words for the sole purpose of keeping things short and to the point. This holds true for most languages (At least if you want readable and maintainable code), but a language like Factor, this becomes an absolute necessity.

I would not be surprised if this is the reason Factor is called Factor. Specifically when related to factoring in Algebra where you do much the same thing: "splitting" an expression into a multiplication of simpler expressions.