Hi Gwladysstreet.
Just a thought but if the setter isn't from around the north of England, maybe they've just plucked the Def from the dictionary and that maybe mentions Newcastle.
I'm at work so can't check my Chambers (hard copy). However, I hear 'mam' often in the North west but the Etymology points towards both the North west and the North east. There is a book called 'A Dictionary of North East Dialect' by Bill Griffiths, 2005, Northumbria University Press, ISBN 1904794165
which may give you more info but the usage notes say
"Used in place of mum or ma in Northumbrian dialects such as Geordie, as well as throughout Ireland and Liverpool"
Hope that helps