exclamation of pain, surprise, wonder, etc., attested by 1916. The number of -o-s may vary. Combined with aah from 1953. Ooh-la-la, exclamation of surprise or appreciation, is attested by 1918, from French ô là! là! and suggestive of the supposed raciness of the French.
France is one fine country and we have been having a pretty good time. The people treat the Americans very well and the pretty girls,--'ooh, la, la!", as they say. ["The Princeton Alumni Weekly," May 29, 1918]