In article , "Harvey Van
Sickle" says...
On 11 Dec 2004, David White wrote

How do you tell the difference between an oil-stone and a wet-stone?

Unless this is a riddle that's gone over my head, the obvious answer is
"You don't, since the latter's a "whet" stone, and you use oil on it".

I suspect whetstone is a general term, covering any bit of stone-like
stuff used for sharpening blades, so could be applied to one using
water, oil or nothing at all as a lubricant/coolant.