'magnetisable' originates from Modern English, specifically from the verb 'magnetise' (UK) / 'magnetize' (US) plus the suffix '-able', where 'magnetise/magnetize' ultimately derives from the noun 'magnet' (from Latin/Greek) and '-able' meant 'capable of'.

'magnetisable' developed as an adjective from Middle English and Early Modern English formations: Greek 'magnētēs' (μαγνήτης) 'lodestone' → Latin 'magnes' → Medieval Latin/French influence 'magnétiser'/'magnetizare' → English verb 'magnetise/ magnetize' → adjective with '-able' yielding 'magnetisable' (UK) and later the US spelling variant 'magnetizable'.

Initially related to the name for the lodestone ('stone of Magnesia') and the action of making something magnetic, it evolved into the descriptive adjective meaning 'capable of being magnetised'.