Mither
To mither is to pester or bother someone, or to fuss and moan; it is a common word in Manchester and the north-west of England. It rhymes with "dither", not "mother".
In practice
"Stop mithering me" means stop nagging; "sorry to mither you" is a polite way to start an email asking for something; "she's mithering about the heating" means she keeps complaining about it. A task or situation can be a mither too: "parking round here is a right mither." The word is old English dialect and is used naturally by people of every background in the region, including in the office.
Why it matters to newcomers
You will see "sorry to mither" in work emails and hear it in meetings, and it is a soft, friendly apology rather than slang. If a colleague says something is "a mither", they mean it is annoying, not difficult.
Related
- Our kid - another everyday northern phrase
- Ginnel - a dialect word for a place rather than a mood
- Mancunian - the people who say it most
Source: Wiktionary: mither.