“Noel” sounds like “no L.” A joke about the “Christmas alphabet” having “no L” has been cited in print to at least 1951. The riddle form is:
 
Q: What’s the difference between the Christmas alphabet and the normal alphabet?
A: The Christmas alphabet has no “L” (Noel).
   
       
Wikipedia: Noel
Noel may refer to:
 
Christmas
. Christmas, from French Noël (“Christmas season”), may come from the Old French nael, may be derived in turn from Latin natalis, meaning “birth”
. Christmas carol, a song sung during Christmas
             
6 December 1951, Chicago (IL) Daily Tribune “Test Your Horse Sense” by George W. Crane, pg. 20, col. 2:
Here is a Christmas puzzle. This pattern of alphabetical letters indicates a yuletide song. What is it?
A B C D E
F G H I J
K M N O P
Q R S T U
V W X Y Z
ANSWERS
Noel [No “L”].
 
21 December 1955, The Christian Science Monitor (Boston, MA), “Little People’s Corner,” pg. 17, col. 7 photo caption:
Christmas Alphabet
The 26 first-graders at the Lincoln School in Monroe, Wis., have their own way of spelling “Marry Christmas.” It may not look that way at first, but look at the little girl standing between K and M. There’s no L (Noel).
         
18 December 1966, Hartford (CT) Courant, “Hints from Heloise,” pg. 9J, col. 2:
And don’t forget there is a new alphabet just published, and it goes ABCDEFGHIJKMNOPQRSTUVWXYZ. Know what’s wrong with it?
 
It has NO “L”. (Noel)
 
23 December 1979, Newsday (Long Island, NY), “Smiles,” Kidsday sec., pg. 1, col. 3:
What Christmas Alphabet goes like this—“A B C D E F G H I J K M N O P Q R S T U V W Y Z?”
“Noel, No-L, No-L. No-L…”
—Tony Roche, Syosset
 
6 December 1986, The Times (Trenton, NJ), “Good Humor,” pg. B1, col. 1:
Jennifer Conners, a 4th grader at George E. Wilson School in Hamilton Township, asks: “In Santa’s Christmas alphabet what letter is missing?”
“No ‘L’.”
 
29 December 1992, Vancouver (BC) Sun, “All about snow,” pg. C9:
Why does the Christmas alphabet have only 25 letters?
No - el.
 
24 December 1994, Newsday (Long Island, NY), “Smiles,” Kidsday sec.:
How many letters are in the Christmas alphabet?
25, no L. (Noel).
Sophia Tantillo, Lynbrook
 
22 December 2007, “Top 10 Websites for Christmas” by Damien Noonan, pg. 22:
What’s different about the Christmas alphabet? It has “noel”!
       
Twitter 
Melitsa Avila‏
@melitsaavila
Q: What’s the difference between the Christmas alphabet and the ordinary alphabet? A: the Christmas one has no L ( Noel). lol
10:20 PM - 12 Dec 2008
 
Google Books
Holly’s Jolly Christmas
By Nancy Krulik
New York, NY: Grosset & Dunlap
2009
Pg. ?:
What’s the difference between the Christmas alphabet and the regular alphabet?
The Christmas alphabet has no L (Noel)
   
Google Books
Horrid Henry’s Hilariously Horrid Joke Book
By Francesca Simon
London, UK: Orion Children’s Books
2014
Pg. ?:
What’s the difference between the ordinary alphabet and the Christmas alphabet?
The Christmas alphabet has No-el.
 
Google Books
Best Christmas Jokes For Kids
By Peter Crumpton
PeteyRF Creative
2015
Pg. ?:
Whats the difference between the Christmas alphabet and the ordinary alphabet?
The Christmas alphabet has Noel.
 
Reddit—Clean Jokes
What’s the difference between the Christmas alphabet and the normal alphabet? (self.cleanjokes)
submitted December 10, 2017 by madazzahatterQuality “Ugh” Contributor
The Christmas alphabet has Noel.