There are a number of us Muldownies (and Muldowneys) in Scotland. The family originated in Ireland pre 1900, but I don'y have any info beyond that.
My grandfather was Thomas Muldowney, married to Elizabeth Duffy. They had 12 children and lived in Shotts, Lanarkshire where my grandfather was a miner.
I know many of the family emigrated to US and Australia in the 1920s and 1930s.