An Etymological Dictionary of the German Language/mucken
mucken, vb., ‘to grumble,’ first occurs in early ModHG., probably akin to late MidHG. mûgen, ‘to roar,’ which may be allied to μυκάομαι, ‘to roar’ (see Mücke). Perhaps it is also connected with Muckser; it is based on MidHG. muckzen, muchzen, OHG. muccazzen, ‘to whisper, grumble’; apparently, however, it is better connected with the Teut. root mū̆k, ‘to pretend to know secrets,’ discussed under meuchel-. To this also belongs the simply ModHG. Mucker, ‘sulky person, grumbler,’ prop. ‘religions hypocrite,’ in which sense the word first appeared in Jena in the early part of the 18th cent. to denote the adherents of the pietist theologian Buddeus.