Another word which is beginning to lose its original meaning is cherub. Originally conceived as huge beings with four wings, four heads, and four hands each, and seeming to be cybernetically linked to golden or flaming chariots, the cherubim used to be pretty impressive angels. The book "A Wind in the Door" offers a wild description of cherubim similar to the Bible, although these are science-fiction versions.

Now, the most common interpretation of the word is "cute angelic child with chubby cheeks and tiny wings". (Exactly like our modern interpretation of Eros, in fact).

One could argue that 'cherub' still refers to an angel, but in my opinion this is a bit of a stretch.

Some more words that were "stolen" (I could have sworn that these were noded before, but maybe that writeup got deleted):

Behemoth - originally meant "beast". Used several times in the Bible, with unclear meaning. I have heard that it refers to hippopotamuses and to whales. Whales, however, have at least one other name in the Bible:

Leviathan - now used to refer to anything that's really, really enormous, leviathan is the Hebrew word for whale. Note that you'll sometimes see this used as an adjective in modern English, as in "a leviathan monster". This is completely wrong. Leviathan is a noun in both Hebrew and English.

Jubilee - Jubilee is a period of fifty years, or a celebration marking that period. Originally there were also lesser jubilees, which were probably seven year periods. Now, of course, we have "Silver Jubilees", which are twenty five year celebrations. The Hebrew word is pronounced "Yovel".