Yours, Etc.: Origins and Uses of 8 Sign-Offs
c.1300, myrke, from Old Norse myrkr "darkness," from Proto-Germanic *merkwjo- (cf. Old English mirce "murky, black, dark; murkiness, darkness," Danish mǿrk "darkness," Old Saxon mirki "dark"); cognate with Old Church Slavonic mraku, Serbo-Croatian mrak, Russian mrak "darkness;" Lithuanian merkti "shut the eyes, blink," from PIE *mer- "to flicker" (see morn). Murk Monday was long the name in Scotland for the great solar eclipse of March 29, 1652 (April 8, New Style).