'chubbiness' originates from English, specifically formed from the adjective 'chubby' + the suffix '-ness', where 'chubby' likely derives from 'chub' (a plump fish) + '-y' meaning 'characterized by'.

'chubby' developed in English (first recorded in the 17th century) from 'chub' (Middle English, a plump fish or a short, fat person), and later the noun-forming suffix '-ness' was added to create 'chubbiness'.

Initially it referred to a resemblance to a 'chub' (i.e., plumpness); over time it came to mean the general state or quality of being slightly fat or pleasantly plump.