A large chunk of
stone or
slate, often shaped like a long, tapered oval for the manual sharpening of tools, from
scythe blades downward. Today, whetstones are manufactured in
Eastern Europe where they are still in greater demand than the
post-industrial West.
The whetstone is also illogically the name of a measuring unit used in computer benchmarking (although running a benchmark could result in an increase of speed in your computer ... specifically that you would see how slow your computer is and be forced to upgrade). This led to the creation (by somebody with no sense of humour or a dictionary) to the words Dhrystone and Khornerstone.
Whetstones also cropped up in the game Betrayal at Krondor, where they could be used to counter the effects of weapon degradation (unsurprisingly).