A search for it on Google seems to indicate it is used in English too:
Yea, gaffe is used in English. Bluelion
- OK, my gaffe then to think it was only used in French :-) D.D. 19:37 May 22, 2003 (UTC)
"goof-up" struck me as bizarre as a translation for "gaffe" since one usually says simply "gaffe". Goof-up is only used on a very informal register of the language, and for any type of error, whether "public" or not. Gaffe (in English) is usually used for an essentially verbal blunder, mainly in politics and public relations, or any blunder of policy. What is not clear to me about the French term is: is it employed, in an informal register, to describe any error, even non-verbal? in which case "goof-up" (or fuck-up) would apply...
gaffe noun An unintentional act or remark causing embarrassment to its originator; a blunder. ORIGIN early 20th cent.: from French, literally boathook (from Provençal gaf:), used colloquially to mean ‘blunder’.