'cell-protective' is a compound formed in modern English from 'cell' + 'protective'. 'Cell' ultimately comes from Latin 'cella' meaning 'a small room, storeroom', and 'protective' comes from Latin 'protegere' meaning 'to cover in front' (from pro- 'before' + tegere 'to cover').

'cell' entered English via Old French/Latin usage as 'cella' and developed into the English word 'cell'; 'protective' derives from the past-participle adjective form of 'protect' (from Latin 'protegere' through Old French 'protecter'), later taking the adjectival suffix '-ive' to form 'protective'. The compound 'cell-protective' is a modern English formation used especially in scientific and medical contexts.

Individually, 'cell' originally meant 'a small room' and 'protect' originally meant 'to cover in front'; combined in modern usage they specifically convey the meaning 'having the quality of protecting cells', a technical/medical sense that developed from general senses of protection and modern biological usage.