Hi Lindsay,
That's some very ambiguous handwriting indeed. My first guess was Crebaugh too, but as you said - that doesn't sound very Irish. It's the fourth letter that's causing problems. Have you tried using alternatives like Crefaugh, Crelaugh, Credaugh, or even a surname that ends with -ough? The conspicuous dot on the "e" might indicate it's an "i" in fact.
Hopefully some of our expert members proficient in handwriting deciphering will jump in with some other suggestions!
Joris