'cankerous' originates from Middle English, specifically the word 'cankrous', where the element 'canker' meant 'ulcer' or 'sore' and the suffix '-ous' meant 'full of' or 'having the quality of'.

'canker' changed from Latin word 'cancer' (meaning 'crab' and by extension 'ulcer') through Old French into Middle English 'canker', and the adjective form 'cankrous' eventually became the modern English word 'cankerous'.

Initially, it meant 'having or relating to a canker (an ulcerous sore)', but over time it evolved to include figurative senses of 'malicious', 'corrosive', or 'spiteful'.