EU all the way, baby. IIRC it showed up back in the OLDold Han Solo novels by Brian Daley.
eta: verified on Wookieepedia, it appeared in the Daley novel Han Solo at Stars' End and was obsolete even then. EU "canon" has it predating the ARC-170.
(RANT ALERT!! If Lucas doesn't want to bother to read what other folks have done in his universe and wants to trample all over the efforts of novel and game writers HIS PEOPLE APPROVED since the first movie came out (Splinter in the Mind's Eye, Lando books, Han Solo books on up to today, including my own humble fan-fic), then he should have NEVER allowed anyone else to write a book with Star Wars in the title. Period. We want a good story. He doesn't take SW as seriously as those (of us) fans who no longer get to play SW Trivial Pursuit because we KNOW THE EFFING ANSWERS - he's said that. We expect a good story - but that carries the requirement of internal consistency across all parts. The folks who write SW fic for the love of SW take the universe damned seriously because we LOVE it! Some authors have gone into rather Twister-ish contortions in order to mesh some potentially contradictory approaches from other writers. And lets face it - WTF is up with the Y-Wing?? They are OLD in SW:ANH! WAY more than 18 years old. The republic should have been operating buttloads of olderish Y-Wings in TPM/AOTC/ROTS, not brand new ones right there at the end of the prequel. Someone doesn't have a handle on military acquisitions.
Oh, and just one more - HAN SHOT FIRST, DAMMIT!! You can't screw with character-defining moments like that and expect to retain credibility...)
