'aftonian' originates from the name 'Afton,' a town in Iowa, USA, where geological evidence of the Aftonian interglacial period was first identified.

'Afton' was used to describe the interglacial period, and eventually, the term 'aftonian' was coined to describe anything related to this period.

Initially, it referred specifically to the geological period, but over time it evolved to describe any characteristic or feature related to this period.