“I bought a knife that can cut through four loaves of bread at once. It’s a four loaf cleaver”

“Four loaf cleaver” is a spoonerism for “four leaf clover.” The jocular “four loaf cleaver” has been cited in print since at least 1948 and 1957.
     
 
Newspapers.com
25 June 1948, Philadelphia (PA) Inquirer, “It’s Happening Here” by Frank Brookhouser, pg. 31, col. 1:
Got mixed up and called Taft’s “Four Leaf Clover” something not so flowery. Called it, in fact, “Four Loaf Cleaver.”
   
14 January 1957, San Francisco (CA) Chronicle, “Talk Around Town” by David Hulbard, pg. 30, col. 1:
Young fellow grabbed four loaves and a bread knife. “Watch,” he cried, “I’m a four loaf cleaver.”
 
Newspapers.com
21 March 1957, Charlotte (NC) News, “Charlotte Close-Up” by Julian Scheer, p. 1-B, col. 1:
Thus being the only man in the world with a four loaf cleaver!
 
Google Books 
Saturday Review
Volume 40  
1957
Pg. 6:
“It sure was,’ said the slicer, “I found a four-loaf cleaver.”
   
Google Books 
Biggest Riddle Book in the World
By Joseph Rosenbloom
New York, NY: Sterling Publishing Company, Inc.
1976
Pg. 242: 
What do you call a knife that cuts four loaves of bread at the same time?
A four-loaf cleaver (clover).
 
Google Books 
April 1981, Boys’ Life, “Think & Grin,” pg. 74, col. 1:
Baker: What do you call a knife that cuts four loaves of bread at a time?
Chef: A four-loaf cleaver.—Henry Roberts, Royston, Ga.
 
Twitter 
Gloson Teh
@Gloson
A man recently invented a knife that cuts four loaves of bread simultaneously. He calls his invention a four-loaf cleaver. <--- LOL!

3:14 AM · Dec 11, 2008·Twitter Web Client
 
Twitter 
PUNS
@omgthatspunny
A long knife has been invented that cuts four loaves of bread at a time called a four loaf cleaver. #punny
9:26 PM · Feb 4, 2012·Timely by Demandforce
     
Reddit—Cleanjokes 
Posted by u/lux514 September 17, 2015
Did you hear about the guy who invented a knife that can cut four loaves of bread at once?
He’s calling it the “Four Loaf Cleaver.”
 
Reddit—Jokes 
Posted by u/Kelly240361 April 4, 2020
I bought a knife than can cut through four loaves of bread at once
It’s a four loaf cleaver