A protocol droid on Cloud City (E-3PO) says this to C-3PO. If C-3PO's reaction is any indication it was either an insult or an obscenity.
Does anyone know a translated version of this word/phrase?
We don't know, but it's very (very) rude.
“E chu ta!” replies the droid.
C-3PO stops, stunned. “How rude!”
(“E chu ta,” is, of course, Huttese. It is absolutely not appropriate to translate. Maybe when you’re older.)
According to wookieepedia, this theme (of the phrase being simply too obscene to translate) is apparently continued in Ben Burtt's 'Galactic Phrase Book and Travel Guide' (the in-universe translator Ebenn Q3 Baoban refused to translate it) as well as in the new 'Star Wars: Legacy' comics where it's simply described as an insult and the old Databank article on E-3PO where his words were referred to as
a scathing invective.