'loose-leaf' originates from English, specifically the words 'loose' and 'leaf', where 'loose' meant 'not tightly fixed' and 'leaf' meant 'a thin flat piece (originally of a plant, later extended to sheets of paper)'.

'loose' comes from Old English 'lūs' meaning 'not tight' and 'leaf' comes from Old English 'lēaf' meaning 'leaf (of a plant)'; the compound 'loose-leaf' developed in modern English to describe sheets that are not bound together and thus 'loose' leaves ('leaf' extended to mean a sheet of paper).

Initially, 'leaf' primarily meant 'a leaf of a plant'; over time it extended to mean 'a sheet (of a book or paper),' and 'loose-leaf' evolved to specifically denote detachable or unbound sheets; 'loose-leaved' is the adjectival form describing that condition.