I never heard the expression “weasel word” before but, after some exploration into the meaning, I find I like it very much. A “weasel word” is one that, on the surface, gives a false impression; it may soften a statement or be downright misleading.
The weasel reference implies sucking the meaning out of the word or phrase, the way a weasel sucks the content out of an egg. It is interesting that sources such as Phrase Finder and Wikipedia suggest weasels can’t or don’t suck eggs, but that didn’t stop Shakespeare from sullying the reputation of the poor little beasts:
I can suck melancholy out of a song, as a weazel sucks eggs. – As You Like It, 1600
In my own writing, weasel words appear as passive voice: “had been”, “will be”, “somewhat”, “evidently”, “possibly”. Eliminate the passive or soft words and phrases and my writing becomes much stronger.
I am; I act; Done!