“What school supply is always tired?”/“A knapsack.”

Do knapsacks take naps? A jocular “daffynition” (daffy + definition) was cited in 1943:
 
“Knapsack: a sleeping bag.”
 
A school riddle has been cited in print since at least 2007:
 
Q: What school supply is always tired?
A: A knapsack!
 
   
27 April 1943, Indiana (PA) Evening Gazette, pg. 2, col. 8:
Add descriptions, for WEAF’s new “Definitions” program: Knapsack: a sleeping bag.
   
Google Books
August 1962, Boys’ Life, “Think and Grin,” pg. 62, col. 3:
Daffynishion: Knapsack — A sleeping bag. — Mike Ulmer, Table Grove, Ill.
 
Google Groups: alt.humor.puns
“Puns of the Weak” 6-2-00
Stan Kegel
6/2/00
(...)
Knapsack: A sleeping bag. (Archives)
   
Jokes Fun Blog
What school supply is
What school supply is always tired?
A knapsack!
Posted by Dirk Sanders on Tuesday, October 9. 2007 at 07:36 in School Jokes
 
Kid Activities
School Jokes & Computer Jokes
June 29, 2009 23:05 by Barbara Shelby
(...)
What school supply is always tired?
A knapsack!
 
Twitter
odds
‏@jokesquotes
what school supply is always tired? a knapsack :o
12:19 PM - 9 Dec 2009
 
Google Books
1001 Kid’s Jokes
By Kay Barnham
London: Arcturus Publishing
2010
Pg. ?:
Which schoolbag is always tired?
A knapsack.
 
Twitter
FabulousSavings.CA
‏@CanadaCoupons
What school supply is always tired? A knapsack! #LunchtimeFunnies
11:45 AM - 5 Sep 2012
   
My Town Tutors
Back to School Jokes: Top Back to School Jokes
Posted on July 1, 2015 by mmolloy
(...)
17. What school supply is always tired?… A knapsack!