'alkali-labile' originates from a combination of the English word 'alkali' and the adjective 'labile'; 'alkali' ultimately comes (via Medieval Latin) from Arabic 'al-qaliy' meaning ashes or soda, and 'labile' derives from Latin 'labilis' meaning 'slipping' or 'likely to fall'.

'alkali' changed from Arabic 'al-qaliy' to Medieval Latin 'alkali' and entered English as 'alkali'; 'labile' changed from Latin 'labilis' through French into English as 'labile', and the two were combined in modern scientific usage to form 'alkali-labile'.

Initially, 'labilis' referred literally to slipping or falling and 'alkali' to ashes/soda; over time the compound came to be used metaphorically in chemistry to mean 'liable to be altered, cleaved, or decomposed under alkaline (basic) conditions'.