“What is the least spoken language in the world?”/“Sign language.”

A language riddle has been printed on many images:
   
Q: What is the least spoken language in the world?
A: Sign language.
   
The joke has been cited in print since at least 2010.
 
     
Twitter   
MelissaTrevizo
@MelissaTrevizo
Dad’s joke of the day, “What is the least spoken language in the world? Answer: Sign Language.” LMAO!!! So stupid its actually smart. XD
7:59 PM · Jul 27, 2010·Twitter Web Client
   
Twitter
Liza Janse v Vuuren
@lizajvv
According to #Census2011: Sign language is the least spoken language in SA. #fact
5:45 AM · Nov 20, 2012·Twitter Web Client
   
Twitter
Ryan
@ryanpaddock28
What’s the least spoken language and where is it used?
Sign language
Around the world.
9:37 PM · Feb 4, 2013·Twitter for iPhone
 
Reddit—Jokes
u/ThatGuyNobodyKnows May 29, 2015
What’s the least spoken language in the world?
Sign language.
   
Reddit—Dadjokes
u/A_Sea_Cucumber September 20, 2017
What is the least spoken language in the world?
Sign language
 
Reddit—Showerthoughts
u/PM-me-girl-nudes November 8, 2017
The least spoken language is sign language.
   
Google Books
Really Bad Dad Jokes:
More Than 400 Unbearable Groan-Inducing Wisecracks Sure to Make You the Funniest Father With a Quip
By Joe Kerz
New York, NY: Simon & Schuster
2019
Pg. 283:
What is the least spoken language in the world?
Sign language.
 
Twitter
Adam Pacitti
@adampacitti
What is the least spoken language in the world?
Sign language.
5:01 PM · Jan 28, 2019·Twitter Web Client
 
Reddit—Jokes
u/richymc9786 September 18, 2019
What’s the least spoken language in the world?
Sign language