The word 'ton' entered English from Anglo-French 'tunne', meaning a large cask or barrel. This term itself derives from Medieval Latin 'tunna', likely of Celtic origin. The semantic shift from a container to a unit of weight is logical, as the weight of a large, full cask of wine became a standard measure. Over time, the spelling simplified to 'ton', and it became the standard term for a heavy unit of mass, with its precise pound-equivalent diverging between the British imperial and US customary systems.

The word 'ton' is a simplex loanword. It does not contain separable morphemes within its modern English spelling.