'adultlike' originates from the English word 'adult' combined with the suffix '-like', where 'adult' refers to a fully grown person and '-like' means 'resembling or similar to'.

'adult' changed from the Latin word 'adultus', meaning 'grown up', and eventually became the modern English word 'adult'.

Initially, 'adult' meant 'grown up', and this meaning has largely remained the same in modern usage.