Atom

 
Most of us know what an atom is – the smallest component of an element having the chemical properties of the element. It is also used in a loose sense to denote any very small particle of something. But did you know the word is centuries old and long pre-dates the discovery of the atom. I only realised that when I found it mentioned in John Dryden’s poem Song for St Cecilia’s Day, 1687...
From Harmony, from heavenly Harmony
This universal frame began:
When Nature underneath a heap
Of jarring atoms lay.

The atom was a unit of time referred to in medieval philosophical writings as the smallest possible division of time.