'sallow' originates from Old English, specifically the word 'sealh' (also written 'salh'), where 'sealh' meant 'willow'.

'sallow' changed from Old English 'sealh'/'salh' to Middle English forms such as 'salwe'/'sallew' and eventually became the modern English word 'sallow'.

Initially, it meant 'a willow (tree)'; over time the word developed an adjective sense referring to a yellowish, unhealthy complexion, while the tree sense remained in certain contexts.