“It’s not over until you shake hands” (hockey, tennis adage)

Tennis players often shake hands at the end of a match. Hockey players in the Stanley Cup playoffs shake hands at the end of a series. “It’s not over until you shake hands” is an adage that has been used in several sports. The saying was cited in print in a 1984 newspaper article about tennis, but an earlier origin is probable.
 
“It ain’t over ‘til it’s over” is a similar saying that was popularized with baseball’s 1973 New York Mets.
           
 
Google News Archive
1 February 1984, Tuscaloosa (AL) News, “Opportunity knocking for Tide tennis team” by Steve Waters, pg. 21, col. 3:
Solis can’t pinpoint why he has that problem, although he realizes better than anyone “It’s not over until you shake hands.”
   
23 May 1988, Springfield (MA) Union-News, “Kask, Kish strike at Oak Ridge” by Jim Regan, pg. 30, col. 1:
“They’re just solid players. But, we kept fighting. We don’t believe a match is over until you shake hands.”
(Golf professional Bill Witaszek.—ed.)
 
8 May 1997, The Orange County Register (Santa Ana, CA), “Ducks Notes” by Cammy Clark and Earl Bloom, pg. Sports 13, col. 5:
“There is still a chance. That’s the thing I think our players have to understand, that it’s not over until you shake hands”
(Detroit Red Wins assistant hockey coach Dave Lewis.—ed.)
 
British Tennis
Madeline
Date: Apr 15, 2007
“This is one of those matches, it’s just not over until you shake hands” lol
 
Orlando (FL) Sentinel 
High school tennis
Spruce Creek advances at state tournament
April 30, 2009|By Colin Brady and Woody Wommack, Special to the Sentinel
(...)
“We both know it’s not over until you shake hands, and we’ve played under pressure all year so we were OK,” Doerfler said.
 
Twitter
Johanna R. Estévez O
‏@Joha_xe
#Wimbledon “...it’s not over until you shake hands…”
7:27 PM - 23 Jul 2011
   
World Tennis
Novak Djokovic Returns To His Winning Ways In Canada, Capturing The Rogers Cup — Mondays With Bob Greene
Posted by Bob Greene on August 16, 2012
(...)
Li Na rallied from a 5-1 third-set deficit to defeat Lucie Safarova in the semifinal so the Rogers Cup, proving the old adage that a match is not over until you shake hands.
 
4 September 2012, Aiken (SC) Standard, “Double bagel win for Serena at U.S. Open” by Rachel Cohen (AP), pg. 2B, col. 3:
“She was fighting really hard,” (Serena—ed.) Williams said. “You give people any type of chance, especially in tennis, the match is never over until you shake hands. There is always a comeback available. So I didn’t want to give her that opportunity -or anyone that opportunity—to come back, especially her in particular.”
   
The Philippine Star
Injured PJ outlasts Jeson
By Olmin Leyba (The Philippine Star) | Updated December 5, 2013 - 12:00am
MANILA, Philippines - PJ Tierro endured an aching ankle and pounced on Jeson Patrombon’s sputtering endgame to emerge victorious in their thrilling marathon encounter, 7-6 (6), 6-7 (3), 7-6 (6), and advance into the quarterfinals of the 32nd Philippine Columbian Association Open yesterday at the PCA courts in Paco.
(...)
“Yun na lang, never say die; it’s not over till you shake hands (It was a struggle. My ankle injury forced me to slice and Jeson was always neutralizing them. It’s really more about never say die spirit),” said Tierro.
 
Twitter
michael scott
‏@DeirdreFanizzi
NO GAME IS OVER UNTIL YOU SHAKE HANDS LETS GO @LadyVol_Sftball WE GOT THIS 🍊
11:08 PM - 23 May 2014
   
Joey Phoenix Photography
February 16, 2015
How 20 Years of Tennis Shaped My Creative Life
Posted on by Joey
(...)
It’s Not Over Until You Shake Hands
Unlike many other sports where critical moments are determined by a set time, a tennis match can go on for hours, sometimes even days. Things can happen quickly, be over fast, or drag on for seemingly forever. Countless times, after 4.5 hours of grueling nonsense, I’d end up in the ER with an IV in my arm. I have chronic fatigue and exercise-induced asthma so my body couldn’t really handle these marathons. Yet, giving up wasn’t really my thing. Again, not because I’m competitive by nature. I just didn’t want to disappoint anybody.
   
The Independent (UK)
Tennis
Wuhan Open 2015: Johanna Konta beats Simona Halep for her finest victory
Konta won 6-3, 3-6, 7-5
PAUL NEWMAN Tennis Correspondent Wednesday 30 September 2015 18:58 BST
(...)
“I wasn’t really thinking ahead or behind,” Konta said afterwards. “I was quite content just to stay in the point that I was playing. I guess there’s a grand old saying: ‘It’s never over until you shake hands.’ I wasn’t actively thinking ‘Yeah, I can win this’ or ‘Oh, it’s over’. I was just trying to stay out there as long as possible and keep fighting on every single point.”