Today I found out why pencil cores are called "lead", even though they don’t contain lead; rather, they are typically made of graphite powder with clay mixed in as a binding agent.
In the 16th century, a large deposit of pure, solid graphite was discovered in Borrowdale, England. This was the first time in recorded history that high quality, solid graphite had been found. When metallurgists first encountered this substance, they thought it was some sort of black lead, rather than a form of carbon. Thus, they called it "plumbago", which is derived from "plumbum", which is Latin for "lead".
Read more here.
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