'ploidy' originates from New Latin combining forms used in biology (the element 'ploid-'), ultimately derived from Greek combining roots such as 'haplous' (single) and 'diploos' (double), where those Greek elements indicated numerical/fold relationships.

'ploidy' developed as a noun in English in the 20th century from biological terms like 'haploid' and 'diploid' (coined in the 19th century using Greek roots). The combining element 'ploid-' from New Latin was adapted into English to form the abstract noun 'ploidy.'

Initially the roots conveyed ideas of 'single,' 'double,' or 'multiple' (numerical/fold), and over time the English term 'ploidy' came to refer specifically to the number of chromosome sets in cells or organisms.