'archaic' originates from Greek, specifically the word 'arkhaikos', where 'arkhaios' meant 'ancient' or 'from the beginning'.

'archaic' passed into English via Latin 'archaicus' and French 'archaïque' from Greek 'arkhaikos', eventually becoming the modern English word 'archaic' and its adverbial form 'archaically'.

Initially, it referred simply to something 'belonging to an earlier period' or 'ancient'; over time it came to be used for things that are 'old-fashioned' or 'no longer in common use', which is how it is commonly used today.