The name Milou is a girl's name . Milou and is often added to lists like Girl Names Uncommon in the US and discussed in our forums with posts like "Heaven/Hell/Purgatory - Newborn girls from the Netherlands".
From the experts:
Milou and her near-identical twin Malou are adorable names popular throughout Europe; they're contractions of Marie or Mary and Lou or Louise. The Malou spelling will probably be easier for English speakers to pronounce; Milou may be conflated with Milo.