I always thought the term "weasel words" derived from the idea that some words are inserted into speech or writing to allow the speaker to weasel out of saying something directly. It turns out it comes from the false belief that weasels suck the insides out of eggs, but leave the shell almost intact, so they appear to have more substance than they do. So in the statement, "I've heard it said that maybe half of your ancestors were kangaroos, just sayin'," the weasel words "I've heard it said," "maybe half," and "just sayin'" suck the hard meaning out of the actual statement "Your ancestors were kangaroos." The speaker, if challenged, can disavow responsibility for the statement, but has still said it.
After reading the Wikipedia article on this, I happened to sit down to edit an application essay by a brilliant, but very shy, student of mine. I found it full of phrases like, "I wanted to," "Although I was," "I believe," "I began to," "I had the opportunity to," and "I helped to." These aren't weasel words mostly, but they serve a similar function. They allow her to say what she accomplished without it seeming like she is saying that she accomplished things. "I designed and carried out the research" reads a lot better than, "I was offered the chance to gain experience in designing research and gathering data," and takes up a lot less space.
The really successful scientists I know not only can say a great deal in very little space, they can squeeze in praise of their own work. I have several times seen, in scientific publications, people describe their own work as startling, revolutionary or subtle. For purely professional reasons, I aspire to this level of unabashidness. For the truly shy, classes in hubris might be in order.