diploma

Diploma comes from Latin diplōma, borrowed from Greek díplōma meaning 'folded paper, license.' That Greek word came from diplóō, 'to double, fold over,' which itself traces to diplóos, 'double.'

The word started as a description of a physical object — a document folded in a particular way — and came to mean the official paper itself, license or certificate, rather than describing its shape.

It shares its root with the idea of 'doubling,' since diplóos meant 'double' before it came to describe a folded, doubled-over sheet.