the word tumour originates from the latin noun tumor, meaning "a swelling," which itself is derived from the verb tumēre, "to swell." this latin root can be traced back to the proto-indo-european base teue-, meaning "to swell," which also gave rise to english words like "thumb" and "thousand," originally conveying a sense of multitude or swelling in number. the term entered middle english via old french tumour, retaining its core medical sense of a morbid swelling. the logic of the word's formation is direct: the root "tum-" captures the essential physical characteristic of the condition, while the suffix "-our" nominalizes it, resulting in the modern meaning of an abnormal growth or mass of tissue.

Structure: tum (swell) + our (noun suffix) tum: from latin tumēre (to swell), origin: latin, functional role: root conveying the core meaning of swelling. our: variant of the latin noun-forming suffix -or, indicating a state or condition, origin: latin via old french, functional role: derivational suffix.