The “club sandwich” is not an acronym, but it is sometimes given the backronym (back acronym) of “Chicken Lettuce Under Bacon.”
 
“Why Club Sandwich? (...) Chicken and Lettuce Under Bacon. That is how it was explained to me” was posted on the newsgroup rec.food.cooking on December 8, 1998. “Waiiit a second…is it called a club sandwich because it’s Chicken and Lettuce Under Bacon?” was posted on Twitter by Brigham Barnes on January 23, 2013. “a CLUB sandwich stands for Chicken and Lettuce Under Bacon #truth” was posted on Twitter by DMP Durham Sharks on March 8, 2013.
 
“No, the ‘Club’ in ‘Club Sandwich’ Doesn’t Stand for Anything” is the title of an article that was posted on The Daily Meal on May 21, 2018.
   
   
Wikipedia: Club sandwich
A club sandwich, also called a clubhouse sandwich, is a sandwich of bread (traditionally toasted), sliced cooked poultry, ham or fried bacon, lettuce, tomato, and mayonnaise. It is often cut into quarters or halves and held together by cocktail sticks. Modern versions frequently have two layers which are separated by an additional slice of bread.
     
Google Groups: rec.food.cooking
Why Club Sandwich?
sarahmelissa douglas
Dec 8, 1998, 3:00:00 AM
Chicken and Lettuce Under Bacon.
That is how it was explained to me.
         
Twitter
Brigham Barnes
@steadilymobbing
Waiiit a second…is it called a club sandwich because it’s Chicken and Lettuce Under Bacon?
2:57 PM · Jan 23, 2013·Twitter for iPhone
   
Twitter
DMP Durham Sharks
@DMP_Sharks
Replying to @WaterlooLadies
@WaterlooLadies a CLUB sandwich stands for Chicken and Lettuce Under Bacon #truth
2:55 AM · Mar 8, 2013·Twitter for iPhone
 
Twitter
Jade Avia
@JadeAvia
CLUB sandwich = Chicken & Lettuce Under Bacon >>> how did I not know that CLUB is an acronym !?!?
5:21 PM · Sep 28, 2014·Twitter for Android
     
Twitter
Jules Ennis D’Alton
@JulesEnnis
So a Club sambo is an acronym of Chicken Lettuce Under Bacon, who knew #mindblown
4:18 PM · Mar 29, 2016·Twitter for iPhone
 
Twitter     
Will Taylor
@Will_Tayls91
I’m 27 and just found out club sandwich means chicken & lettuce under bacon - mind blown
10:52 AM · May 14, 2018 from Wandsworth, London·Twitter for iPhone
 
The Daily Meal
No, the ‘Club’ in ‘Club Sandwich’ Doesn’t Stand for Anything
May 21, 2018
ByJeremy Rose
But we won’t judge you for putting the chicken and lettuce under the bacon if that’s how you roll
 
Reddit—Showerthoughts
Posted by u/Magic_Bluejay May 8, 2019
A club sandwich is actually a Chicken and Lettuce Under Bacon.
 
Twitter
lauren ✰ laurdiy.eth
@laurDIY
I was today years old when I learned a club sandwich stands for chicken lettuce under bacon
1:09 AM · May 27, 2019·Twitter for iPhone
   
Reddit—IsitBullshit
Posted by u/dtr97 August 10, 2019
IsItBullshit: “Club” sandwich is an acronym: chicken lettuce under bacon ?
 
Twitter
Maggie Howell
@Mar__G_3
I just found out the “club” in club sandwich means “Chicken Lettuce under Bacon”...I am speechless
11:09 PM · May 9, 2020·Twitter for iPhone
       
Twitter 
Marco Baril
@MarcoBaril
Replying to @caspeupas
Chicken lettuce under bacon ; C.L.U.B
6:36 PM · Dec 28, 2021·Twitter for iPhone
 
Twitter
SISTO⛓Pawns Corpse EP OUT NOW
@sisto_official
A CLUB SANDWICH IS CHICKEN, LETTUCE, UNDER, BACON. WHY DID I NOT KNOW THIS UNTIL NOW.
1:45 PM · Jan 5, 2022·Twitter for iPhone
 
Twitter
Ollie and Dave.
@BeachDog15
Having a BLT sandwich. Did you know the club sandwich was named after its ingredients also. Chicken and lettuce under bacon?
7:33 AM · Jan 14, 2022·Twitter for iPhone
 
Twitter
E. Harvie Ward
@MingMizuno
Replying to @chrismccork @Broonjunior and 2 others
Club Sandwich
Chicken
Lettuce
Under
Bacon
Science.
10:19 AM · Jan 15, 2022 from Glasgow, Scotland·Twitter for Android