Arnie is of German origin and means 'eagle power'. It's often used as a short form for Arnold, but it can also stand alone. Historically, it has been more popular in the United States than elsewhere.
"Arnie has seen a significant rise and fall in popularity over the past century and a half. Peak years include 1958 (52 births) and 1957 (47 births), while more recent years have seen fewer than 10 Arnie births annually."