potassium

Coined in 1807 by British chemist Humphry Davy, who built the word from potassa, a Latinized form of potash, adding the chemical suffix -ium.

The word was created at the moment of discovery, giving Davy's new element a name in one stroke rather than borrowing an old one.

It shares its root with potash itself, the substance Davy started from when he named the element.