'fleece' originates from Old English, specifically the word 'flēos' (or related forms), where it meant 'wool, fleece (of a sheep)'.

'fleece' changed through Middle English forms (e.g. 'fles') and eventually became the modern English word 'fleece'. The verb sense 'to strip the fleece from' developed from the noun sense, and the figurative sense 'to cheat or strip someone of money' arose later.

Initially, it meant 'the wool of a sheep', but over time it evolved by metaphor to mean 'to strip (something) away' and then 'to cheat or swindle someone', its current figurative meaning.