In the world, Macmillen (Macmillen 
) is an extremely rare boy's first name. Much more frequently, Macmillen is the last name as well as the forename.
Mr, Eric, Hugh, Iris, Maeve, Mikel, Sarah, Susan, Stacy, Scott, Alysa, Clare, Barry, Kathy, Kelly, Kevin, Peter, Rowan, Dewey, David, Dayna, Donna, Neal, Gavin, Nora, John, Ann, Ada, Don, Ian, Xan, Marc, Mary, Matt, Sean, Alec, Adam, Bill, Kate, Paul, Dana, Gwen, Lisa, Lori, Lynn, Jade, Josh, Nina, and Grace