'archplagiary' originates from two elements: the prefix 'arch-' from Greek, specifically the element 'arkh-'/ 'archo-' where 'arkhē' meant 'chief' or 'ruler', and 'plagiary' which originates from Latin, specifically the word 'plagiarius' where 'plagiarius' meant 'kidnapper' (later used of literary theft).

'plagiary' changed from Latin 'plagiarius' (meaning 'kidnapper' or 'one who steals people') into Late Latin and Medieval Latin senses of 'literary thief,' and through Middle English it gave English 'plagiary'; adding the Greek-derived prefix 'arch-' produced the compound 'archplagiary' to mean 'chief/extreme plagiarist.'

Initially, the root 'plagiarius' referred to 'kidnapper' or 'one who stole people'; over time it evolved to mean 'literary thief' and the compound 'archplagiary' came to mean the 'extreme' or 'chief' form of such a thief.