Blackstone

Part of speech: noun

Definitions

1. A fine-grained dark stone historically used to sharpen knives, tools, and blades to a keen edge
2. A dark stone with a smooth surface traditionally employed for honing and polishing metal implements
3. A hard dark rock traditionally used as a whetstone for sharpening cutlery and other bladed tools

Etymology: Blackstone is about as transparent as English compounds get: Old English "blac" (black) joined with "stān" (stone). Its interest lies less in the parts than in what the compound names. It is a plain descriptive coinage from the early English stock of words, built from two of the most basic vocabulary items in the language, with no borrowing from Latin, French or Greek involved. The compound's sense rests on the ordinary colour of the stone rather than any special property. Whatever it denoted in Old English, the word has survived as a straightforward descriptor, and its two roots remain the same everyday words they were more than a thousand years ago.