Similar to OMG (Oh my god!), but ending with a fashionable "osh" to imply "Oh my gosh!", which isn't "Oh my god!", which is important, if importance was the issue. Which it's not.
It's like omg, but better, because it involves gophers. See omgooses. If you're not the goose-type, try a gopher. Gopher's may be a rodent and or pest, but that gopher was one hell of a character in Caddyshack I.