BROCKTON, Mass.--(BUSINESS WIRE)--HarborOne Bank has completed its acquisition of Merrimack Mortgage Company, Inc. of Manchester, N.H. – a privately held home loan originator that averages more than $1 billion in annual business throughout New England. By acquiring the privately-held home loan originator, HarborOne will significantly increase the size of its mortgage business and secure a foothold in key lending markets in the New England region. Merrimack will become a wholly-owned subsidiary