'pentyl' originates from 'International Scientific Vocabulary', specifically from 'pentane' with the suffix '-yl', where 'pent-' meant 'five' and '-yl' indicated a radical derived from a hydrocarbon.

'pentyl' was formed in the 19th century as chemists began systematically naming hydrocarbon radicals, and it became the standard term in modern organic chemistry.

Initially, it meant 'the radical derived from pentane', and this meaning has remained unchanged in modern usage.