“Dijon vu” (dijon mustard + deja vu) is a jocular formation meaning “the same mustard as before.” The term “dijon vu” has been infrequently used and is rarely spoken, but has appeared as a popular Internet joke since at least November 1993.
     
   
Urban Dictionary
dijon-vu
the feeling you’ve seen that same mustard before.
I am having dijon-vu.
by a_falling_toilet Nov 26, 2003
   
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From: .(JavaScript must be enabled to view this email address) (Leigh Melton)
Date: 31 Jan 93 20:19:00 GMT
Subject: Auto Insurance
 
Dijon vu: the feeling you’ve tasted this mustard before.
   
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From: .(JavaScript must be enabled to view this email address) (Ray Wade)
Date: Mon, 27 Jun 1994 22:35:00 GMT
Subject: Best dual-band HT antenna
 
Dijon vu: Have I had this mustard before?
 
1 April 1995, Daily News-Record (Harrisonburg, VA), “More Word Play” by Jim Bishop, pg. 18, col. 3:
Dijon vu: the feeling you’ve tasted this mustard before.
 
19 August 1996, Garden City (KS) Telegram, “E-mail philosophers go Online” by Dolores Hope, pg. 4, col. 1:
Dijon vu: the feeling you’ve tasted that mustard before.
 
Google Books
They Snooze You Lose:
The educator’s guide presentations
By Lynell Burmark
San Francisco, CA: Jossey-Bass; Chichester: John Wiley [distributor]
2011
Pg. ?:
Dijon vu—the same mustard as before