Word Origin & History
mull (v.1)
"ponder," 1873, perhaps ult. from M.E. mullyn "grind to powder, pulverize," from molle "dust, ashes, rubbish," probably from M.Du. mul "grit, loose earth," related to mill. But Webster's (1879) defined it as "to work steadily without accomplishing much," which may connect it to earlier identical word in athletics sense of "to botch, muff" (1862).