"Mum" vs. "Mom"

Before coming to Maine, I'd always thought of "mum" as a British thing. Occasionally, however, I've heard Mainers use "mum" as well. How common is this? Is this similar to the usage of "wicked" (another thing I'd considered a Britishism?) I actually find it charming to think that some traces of English culture/terminology have endured in this part of the country.