Skittish

What's "skittish?" It's an adjective meaning easily excitable.  We frequently use it about an animals--many horses are skittish--but we also use it to describe people.  Today, for example, one story reported that investors are skittish--selling and buying stocks nervously--over the debt crisis in Greece.

And where does the word come from?  Nobody knows for sure, though it may be from Old Norse.  So it's like a lot of words in English: we often don't know the origin of the words we use everyday!  But no matter where it comes from, it's a good word to know.....