'ascomycetal' originates from New Latin, specifically the word 'Ascomycetes', where 'asco-' (from Greek 'askos') meant 'sac' and '-mycet'/'-mycetes' (from Greek 'mykēs') meant 'fungus'.

'ascomycetal' developed as an English adjective from the New Latin 'Ascomycetes' and the related adjective form 'ascomycetous', eventually yielding the modern scientific adjective 'ascomycetal'.

Initially it designated relation to the group named Ascomycetes (sac fungi); over time it has remained a specialized adjective meaning 'relating to sac fungi' in scientific contexts.