Yours, Etc.: Origins and Uses of 8 Sign-Offs
"side of bacon," Middle English flicche (early 13c.), from Old English flicce, related to Old Norse flikki, Middle Low German vlicke "piece of flesh." Not immediately connected to flesh (n.), but perhaps from the same PIE root. A flitch was presented every year at Dunmow, in Essex, to any married couple who could prove they had lived together without quarreling for a year and a day, a custom mentioned as far back as mid-14c.