'alkali-stable' is a modern English compound formed from 'alkali' + 'stable', where 'alkali' came into English via Medieval Latin/Old Spanish from Arabic 'al-qaly' meaning 'ashes of saltwort' (used to make lye) and 'stable' derives from Latin 'stabilis' meaning 'firm, steady'.

'alkali' entered European languages from Arabic 'al-qaly' (literally 'the ashes') into Medieval Latin/Spanish and then English as 'alkali'; 'stable' came from Latin 'stabilis' via Old French/Old English 'stable' and the two were compounded in modern scientific/technical English to form 'alkali-stable'.

Originally 'alkali' referred specifically to plant ashes or lye; over time it broadened to mean basic (high pH) substances. 'Stable' originally meant 'standing firm' and has retained the sense of resistance or permanence; together the compound now specifically denotes resistance to alkaline conditions.