'ascidiae' originates from Latin, specifically the word 'ascidia', where 'ascidia' ultimately comes from Greek 'askidion' (a diminutive of 'askos') meaning 'little bag'.

'ascidiae' changed from Latin 'ascidia', which derived from Greek 'askidion', and entered modern scientific English usage as the Latin plural form used in taxonomy ('ascidiae').

Initially it referred to a 'little bag' (the Greek root), then was applied as a name for sac-like marine animals, and now functions as the scientific plural referring to those sea squirts.