Check tomorrow's post for a satirical April Fool's etymology. The word fool today means "a silly or unwise person". This was phonetically very similar throughout its career in English, but it definitely changed semantically. Back in the fifteenth century, any "silly" person was frowned upon as indecent, since they were all serious folks back then. Many indecent persons were prostitutes, and so was the word fool: it used to mean "sex worker". Sadly, as you go back in history, this curious usage fades: this came from the Old French word fol, which meant "idiot", much closer to our current definition. This in turn is from Latin follus, "foolish", from the earlier Latin word follis, which meant "bellows" (as in the thing you use to waft a fire; the meaning applied to follus was metaphorical and implied an empty windbag of a person), from follicus, "a little bag" (the source of the scientific term follicle today, directly). This is from the root follis (completely different from the later one; don't confuse the two) which had to do with inflating stuff, from the Proto-Indo-European root bhel, or "to swell". Because of how foolish people manipulated language, a fool has thus been "a clown", a "prostitute", and a "bag". LANGUAGE IS AWESOME.
Adam Aleksic has been described as the internet's sixth most famous etymologist. He loves writing about himself in the third person, he's a freshman at Harvard University, and he has disturbing interests in linguistics, vexillology, geography, board games, limericks, and law.
The Etymology Nerd