'actipylea' originates from Greek, specifically the word 'aktis' meaning 'ray' and 'pyle' meaning 'gate', referring to the radiating structure of their shells.

'actipylea' changed from the Greek word 'aktispylea' and eventually became the modern English word 'actipylea'.

Initially, it referred to the radiating structure of their shells, and this meaning has largely remained the same in modern usage.