'actinula' originates from New Latin, specifically the word 'actinula,' where 'actin-' referred to 'ray' or 'radiating structure.'

'actinula' changed from the New Latin word 'actinula' and has remained largely unchanged in modern English.

Initially, it meant 'a small ray-like structure,' but over time it evolved into its current meaning of 'a larval stage of coelenterates.'