Where does “socage” come from?

socage (Old French) comes from Old French soc, from Vulgar Latin soccus, from Proto-Celtic sukkos, from Proto-Indo-European suH-, from Proto-Indo-European sewH-, from Proto-Indo-European sew- — to press out, extract; juice; liquid, rain; to...

socage (Old French): socage (system whereby a tenant would pay a rent or do some agricultural work for the landlord)