'animalculum' originates from New Latin, formed from Latin 'animal' plus the diminutive suffix '-culum,' meaning 'little (thing)'.

'animalculum' entered English from New Latin largely unchanged, used by early microscopists to describe tiny living creatures seen through the microscope.

Initially, it meant 'a little animal,' and it came to refer specifically to microscopic organisms; the term later fell out of common scientific use, replaced by 'microorganism' and 'microbe'.