Nadya-

>Before Nancy's explanation I thought, that it's an short form of "function". Anyway, I personally hate to see all these "foo"s in my colleague's code. I always use a meangful name for variables, objects, etc., even for temp variables.

Actually, that's the point. It's used when there is no meaningful name. IOW, coming up with a name with meaning would distract from what is being communicated.

So far as I know it's never used in real code, by good programmers, unless it's just forgotten. It's almost always used in examples.