'tree-dweller' originates from Modern English, specifically the compound 'tree' + 'dweller', where 'tree' meant 'a woody plant with a trunk' and 'dweller' meant 'one who dwells'.

'dweller' changed from Old English roots such as 'dwelian'/'dwellan' and Middle English forms of 'dwell' plus the agentive suffix '-er' to form 'dweller'; 'tree' comes from Old English 'trēow' (later 'treo'), and the compound 'tree-dweller' developed in modern usage by combining these elements.

Initially it meant 'one who dwells in a tree' in a literal sense; over time the term has kept this core meaning and has also come to be used in biological contexts to denote arboreal species and occasionally in figurative or descriptive speech.