Mither

Closely associated with Manchester and the wider North West, used for someone going on and on until they've become a genuine nuisance ("stop mithering me"). Recorded since the 1840s, it's treated by the Oxford English Dictionary as a variant of the older word "moider," a chiefly Irish, Manx, and Northern English word meaning to confuse, bewilder, or wear someone out. "Moider" itself is of uncertain origin, possibly from Irish "modartha" (dark or murky), which leaves "mither" resting on an etymology that's already a guess one layer down.