'animalcules' originates from New Latin, specifically the word 'animalculum,' where 'animal-' meant 'living being' and the diminutive suffix '-culum' meant 'little'.

'animalculum' transformed into French 'animalcule' and then into English 'animalcule'; the English plural 'animalcules' became established in early scientific English.

Initially, it meant 'little animal,' but over time it came to denote 'microscopic organism' in early microscopy discourse, now used chiefly in historical or archaic contexts.