Gaa-Gew! Is a word that is used to replace the word "Good God" when around small children or when you just dont want anyone to understand what the heck your saying because of something silly or ridiculous they did! My sister came up with this word because she is a Kindergarten teacher and when the kids have those "good god" moments she couldnt say "good god" in school, so she had to come up with something fun so the kids wouldnt understand what she was thinking or saying!
Imagine someone picking their nose right in front of you! Now what would you say to that? "GAA-GEW!!!"