'allele' originates from the German word 'Allel,' which is a short form of 'allelomorph,' where 'allelo-' meant 'each other' and '-morph' meant 'form.'

'Allel' was adopted into English as 'allele' in the early 20th century.

Initially, it referred to any of two or more forms of a gene, and this meaning has remained consistent in modern usage.