It depends on the size schnauzer but popular names are often German ones. Schatzie meaning little sweetheart, Zucker meaning sugar, or given names such as Edith, Hilda, Helga, Gertrude, Gus, Hans, Fritz, Frans and Baron.
Typically the smaller miniature schnauzer is given the 'cuter' type names while the standard and giant schnauzer might get a more regal sounding one.
Schnauzer is from the German word "schnauze" which means "nose". German-sounding names like Hans, Fritz and Wolfgang would be good for a boy, or Heidi or Gretel for a girl.
Some good names for Schnauzers are Roscoe, Wilson, Scruffy, Bandit, Onyx, Scooter, Salty, Scrump, Mac, Max, Grover, Gunther, Pepper, Snitzel, Phoebe and many more.
Any name that suits your dog's personality would be a good name. I prefer unique names so that every dog in the neighborhood doesn't respond when you call your pooch.