The german word for corpus christi is Fronleichnam where Fron stands for ‘unpaid work of serf and servant peasants for the landlord or landlord in feudalism’. Middle High German „vrōn (e)“, that language level of German that was spoken between 1050 and 1350 in Upper and Central Germany, is a substantiation of the Middle High German adjective „vrōn“ ‚which refers to the, spiritual or secular, gentleman that belongs to him, holy‘.
The religious-christian use of the adjective is preserved in Corpus Christi. It is called ‘the body of the Lord, the body of Jesus Christ’, from Middle High German vrōnlīcham, vrōnlīchname, according to Middle High German vrōne līcham.
„Corpus Christi“, in: Wolfgang Pfeifer et al., Etymological Dictionary of German (1993), digitized and revised by Wolfgang Pfeifer version in the Digital Dictionary of the German Language, accessed on May 31, 2021.