'tailless' originates from Middle English, specifically the word 'tail' combined with the suffix '-less', where 'tail' meant 'the rear appendage of an animal' and '-less' meant 'without'.

'tail' combined with '-less' in Middle English to form 'tailless', and this has remained largely unchanged in modern English.

Initially, it meant 'without a tail', and this meaning has largely remained the same in modern usage.