From The Annotated Fall:

“Mithering” is a northern British slang term which is basically equivalent to “whining,” or to the still British but more familiar “whinging.” As for the rest of the title, in a handwritten note reproduced on the Fall online forum, MES explains:

“C ‘n’ C= Cash and Carry, abbreviated as that sounds too corny. S. = stop. N.B. C ‘n’ C is like that too as it’s a pun on C ‘n’ N or C ‘n’ W.”

“C ‘n’ N” stands for “Country and Northern,” a play on “C ‘n’ W”/ “Country and Western.” Country and Northern is a term MES was using to describe the band’s music at this time, as they were beginning to incorporate elements of both country music and rockabilly into their sound.

The song’s title is also a cipher: “C ‘n’ C-S Mithering.”