Friedrich

masc. proper name, from French Frédéric, from German Friedrich, from Old High German Fridurih, from Proto-Germanic *frithu-rik, literally "peace-rule," from *rik- "rule" (from PIE root *reg- "move in a straight line," with derivatives meaning "to direct in a straight line," thus "to lead, rule") + *frithu- "peace" (source also of Old English friðu "peace, truce"), from suffixed form of PIE root *pri- "to be friendly, to love."

Related to the first half of Friday and the second half of afraid, also the second element in Siegfried, Godfrey, Geoffrey. Not a common name in medieval England, found mostly in the eastern counties.