'alkali-resistant' is a compound formed from 'alkali' + 'resistant'. 'Alkali' comes into English via Medieval Latin/Old Spanish from Arabic 'al-qaly' meaning the ashes of saltwort used to make soda. 'Resistant' derives from Latin 'resistere' meaning 'to stand back, oppose'.

The element 'alkali' entered English from Arabic 'al-qaly' through Medieval Latin/Old Spanish and came to mean 'basic (as opposed to acidic) substances.' 'Resistant' evolved from Latin 'resistere' through Old French and Middle English. The modern compound 'alkali-resistant' arose in technical/materials contexts in modern English by joining these two elements.

Initially 'alkali' referred more narrowly to soda/ash obtained from plants; over time it broadened to mean substances with basic (high pH) chemical properties. 'Resistant' originally meant 'to stand back' or 'oppose' and evolved into the sense 'not affected by' in contexts like materials and biology; together they now mean 'not affected/damaged by alkalis.'