Semaphore has led to several puns about “flagging.” “I tried semaphore as a twitter alternative today.  But after an hour or so I was flagging” was posted on Twitter by John V Willshire on August 2, 2011. “I once did a semaphore marathon. After 12hrs I was flagging” was posted on Twitter by Matt Stanley on December 25, 2011. “It took me 6 hours to learn basic semaphore. After that I was flagging. #1Pun” was posted on Twitter by Richard Pulsford on April 3, 2018.
   
Stand up comedian Richard Pulsford told this joke at the 2019 Edinburgh Festival Fringe, where it was voted one of the top ten jokes:
   
“After learning six hours of basic semaphore, I was flagging.”
   
     
Wikipedia: Flag semaphore
Flag semaphore (from the Greek σῆμα, sema, meaning sign and φέρω, phero, meaning to bear; altogether the sign-bearer) is the telegraphy system conveying information at a distance by means of visual signals with hand-held flags, rods, disks, paddles, or occasionally bare or gloved hands. Information is encoded by the position of the flags; it is read when the flag is in a fixed position. Semaphores were adopted and widely used (with hand-held flags replacing the mechanical arms of shutter semaphores) in the maritime world in the 19th century.
     
Twitter
John V Willshire
@willsh
I tried semaphore as a twitter alternative today.  But after an hour or so I was flagging.
2:05 PM · Aug 2, 2011·Twitter for iPhone
   
Twitter
Matt Stanley
@mattystan1972
I once did a semaphore marathon. After 12hrs I was flagging.
9:47 AM · Dec 25, 2011·Twitter for Android
   
Twitter
Kensington Gore
@Kensington_Gore
@vampyregod666 I didn’t know I used to do an act with semaphore but after 1st round I was flagging 😉
4:45 PM · Jun 8, 2013·Twitter for iPhone
   
Twitter
Neil James
@JesseJames150
I entered a 24 hour semaphore marathon recently. After 20 hours I was flagging badly.
12:41 PM · Jul 16, 2014·Twitter for Android
   
Twitter
Richard Pulsford
@RichardPulsford
It took me 6 hours to learn basic semaphore. After that I was flagging. #1Pun
8:00 AM · Apr 3, 2018·Twittimer
   
Twitter
mark gorman
@markagorman
After learning six hours of basic semaphore, I was flagging. by
@RichardPulsford best of the top ten
@edfringe gags IMHO.
7:34 PM · Aug 18, 2019·Twitter Web App
 
BBC News
Vegetable joke is funniest gag at the Edinburgh Fringe
August 18, 2019
(...)
Best of the rest
Ten jokes made the 2019 shortlist. Here are the next nine:
(...)
“After learning six hours of basic semaphore, I was flagging - Richard Pulsford
 
Reddit—Jokes
Posted by u/dr_pr August 19, 2019
10 best one-liners from the 2019 Edinburgh fringe
“I keep randomly shouting out ‘Broccoli’ and ‘Cauliflower’ - I think I might have Florets”.
The gag won 41% of the vote.
Best of the rest
Ten jokes made the 2019 shortlist. Here are the next nine:
(...)
“After learning six hours of basic semaphore, I was flagging - Richard Pulsford