Mee-mawing was a form of speech with exaggerated movements to allow lip reading employed by workers in weaving sheds in Lancashire in the nineteenth and twentieth centuries. The noise in a weaving shed rendered hearing impossible so workers communicated by mee-mawing which was a cross between mime and lip reading. To have a private conversation when there were other weavers present, the speaker would cup their hand over their mouth to obscure vision. This was very necessary as a mee-mawer would be able to communicate over distances of tens of yards. It was said that each mill had its own dialect.
"Stop mee-mawing at me!" means "Stop pulling faces at me or talking behind my back!"
References
Mee-mawing Wikipedia(Text) CC BY-SA