'tree-living' originates from Modern English, specifically the words 'tree' and 'living', where 'tree' meant 'woody plant' and 'living' meant 'being alive'.

'tree' changed from Old English 'trēow' (also written 'treow'), which referred to a woody plant, and 'living' comes from Old English verbs and nouns related to 'libban'/'līf' (to live, life); the compound 'tree-living' was formed in Modern English by combining these elements to describe organisms or lifestyles that live in trees.

Initially, the components meant 'woody plant' and 'being alive'; combined, they described 'living in trees', and over time the compound has retained that core sense of 'inhabiting or living on trees'.