Tennis star Andy Murray fell victim to a curious sporting clash of cultures as his Australian Open victory was greeted by a constant round of "Siiiu" shouts.
Fans at the Rod Laver Arena were in full voice while the Scot downed Nikoloz Basilashvili in the first round of the Grand Slam.
Both he and local favourite Nick Kyrgios were bemused by the chant - but why did it take hold?
Why are fans saying 'Siiiu' at the Australian Open and what does it mean?
Frankly, it is impossible to know just why the 'Siiiu' chant has taken hold at the Australian Open this year.
Yet its 'inventor', Cristiano Ronaldo, is one of the world's most famous sportsmen, and the phrase has become synonymous with the Manchester United star, who often screams it out as he celebrates.
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As for its meaning, it is simply "yes" in Ronaldo's native Portuguese, albeit with the sound exaggerated and prolonged for extra dramatic effect.
Why does Cristiano Ronaldo say 'Siiiu'?
"The scream? The players know I always do that shout when I score a goal or when we win," Ronaldo told Spanish TV station Cuatro on one occasion when asked about his catchphrase a number of years ago.
"It’s our shout, from Real Madrid."
What has Andy Murray said about 'Siiiu'?
Murray, on the other hand, was less than impressed.
"Initially, I thought it was, because there were some people booing during my practice yesterday. I have no idea what for," he told reporters.
"But then after a few times it was like, 'No, they're doing that, I think it's like 'Siuu' or something that Ronaldo does when he scores. And, yeah, it was incredibly irritating."
The flamboyant Kyrgios offered a more colourful evaluation: "It's just a stupid [chant], f*ck, I can't believe they did it so much.
"They were doing some Ronaldo thing. Ronaldo does it every time he scores. It's like - I thought they were going to do it for 10 minutes.
"They did it for two-and-a-half hours, like every point. I don't know why. It was a zoo out there."
Daniil Medvedev, the highest ranked player in the men's draw in Australia, was also unimpressed, saying that the shout was "disrespectful" and those doing it "probably have a low IQ".