And GOAWAY is not clear and understandable from its name?
If we're really talking clear and understandable, id wager more of the world would understand FUCKOFF than it would GOAWAY, for example.
English profanity has a tendency to be better understood by other languages and countries than the appropriate western vernacular.
GOAWAY makes plenty sense when compared to GTFO, assuming that not everyone who learns of it intentionally is well-versed in that of which GTFO is a relatively smaller part. Grandma wouldn't necessarily get GTFO (right away, anyway) but she would likely pick up GOAWAY in a snap.
Of course, the above assumes a section of people who are fluent (enough?) in English to grok the spec.
EDIT: Grammerr.
EDIT: Clarification in response to Vonmoltke.