I can’t say about pre Vatican II and I know that at one time there was the practice of not eating meat on Wednesday’s, but if it’s like the no meat on Friday rule then it’s a for of penance. I know the Church recognizes that Wednesdays and Fridays are days of penance.
I think that possibly it relates back to “spy wednesday”. . .the date traditionally that Judas sold Jesus to the sanhedrin for the 30 pieces of silver, the day before Holy Thursday. To me it seems like a penitential practice.
I have never heard the term “Spy Wednesday” before. But it does make sense that fasting on Wednesday would be linked to the penance for Judas’ betrayal.
DISCLAIMER: Catholic Answers has turned over the archive to Catholic-Questions.org and no longer owns, manages, or moderates the forums. For additional apologetics resources please visit www.catholic.com.