'resguardar' originates from Spanish, specifically formed from the prefix 're-' + the verb 'guardar' (from Old French 'guarder'), where 're-' meant 'again/back' and 'guardar' meant 'to guard' (ultimately from Proto-Germanic *wardōn 'to watch, guard').

'guardar' changed from Old French 'guarder', which came from Frankish *wardōn, and eventually became Spanish 'guardar'; 'resguardar' developed later by prefixing 're-' to 'guardar'.

Initially it meant 'to guard or watch', but over time it evolved into its current sense of 'to protect, to safeguard'.