'protozoan' originates from Greek, specifically the words 'prōtos' meaning 'first' and 'zōion' meaning 'animal', referring to the idea of 'first animals' or primitive life forms.

'protozoan' was coined in the 19th century from the Greek roots and became the standard term in biology for single-celled eukaryotic organisms.

Initially, it meant 'first animals' or primitive forms of animal life, but now it refers specifically to a group of single-celled eukaryotic organisms.