'unacclimatized' originates from the prefix 'un-' meaning 'not' and the word 'acclimatize,' which comes from the French 'acclimater,' meaning 'to get used to a climate.'

'acclimatize' changed from the French word 'acclimater' and eventually became the modern English word 'acclimatize.'

Initially, it meant 'to get used to a climate,' and this meaning has largely remained the same in modern usage.