'asellus' originates from Latin, specifically formed from the word 'asinus' with the diminutive suffix '-ellus', where 'asinus' meant 'donkey' and '-ellus' meant 'little'.

'asellus' is attested in Classical and Medieval Latin as the diminutive of 'asinus' and was later adopted into modern scientific nomenclature as the genus name 'Asellus' for certain freshwater isopods.

Initially it meant 'little donkey' in everyday Latin; over time the form was preserved in scholarly and scientific contexts, where it now also functions as a technical/proper name for a genus of crustaceans.