'ascidiform' originates from Neo-Latin, specifically the word 'ascidium', which itself comes from Greek 'askidion', where 'askidion' meant 'little bag'.

'ascidiform' developed as an English adjective by combining Neo-Latin 'ascidium' (or the stem 'ascidi-') with the suffix '-form' (meaning 'shape' or 'form'), yielding the modern word 'ascidiform'.

Initially it referred specifically to the form of an 'ascidium' (a small sac or the body of an ascidian), and over time it has come to mean more generally 'sac-shaped' or 'pouch-like'.