You might be right. You could argue Master does have a homonym, as "Authority over thing" comes from Latin origins in "magister" while "Full proficiency at a sk

You might be right. You could argue Master does have a homonym, as "Authority over thing" comes from Latin origins in "magister" while "Full proficiency at a skill" comes from the French "maistre". But they more or less came to mean the same thing in English. To say someone has "Authority over a skill" embodies the meaning of both at once as an example. Digging into the usage of Master for "Master Copy" you could say the intention is that the master copy has authority, or highest standing, over all other copies, so more or less the meaning they were trying to avoid.