Odds are you've noticed that Manchester City striker Sergio Aguero doesn't have his first name printed on the back of his shirt – instead having "Kun" emblazoned on his kit.
The Argentina international is the Etihad club's top-scorer and has permanently etched his name into the club's history, starting from when he netted that memorable stoppage-time goal against Queens Park Rangers in 2012 to secure the title at the death.
So why does Aguero go by "Kun" instead of his first name? Goal takes a look.
Why does Sergio Aguero go by "Kun"?
Augero is nicknamed "Kun" and has the name "Kun Aguero" printed on the back of his shirts instead of "Sergio Aguero".
The reasoning for the nickname dates back to his childhood, revealing that it was actually his grandfather who chose the name for him after a Japanese cartoon character called "Kum-Kum", who liked to create trouble.
"Kun actually represents a Japanese cartoon character from my favourite series that I used to watch as a child," Aguero had told the BBC.
"I coined the nickname Kun because of my resemblance to the character, who was actually named 'Kum Kum'.
"My grandparents were the first ones who gave me the name. I think my nickname is different in comparison to most athletes and so I have grown to appreciate it because it's unique. It's not everyday an athlete is nicknamed after a cartoon character!"
In addition to the relation to the Japanese cartoon character, in Japanese language honorifics, the word "Kun" is used to address mostly men and young boys. It is a term used by superior figures to inferiors, males of the same age and status to each other, and addressing male children.
Schoolteachers, for instance, will typically address male students with "kun" while female students are addressed as "san" or "chan".
According to Premier League rules, Aguero was allowed to have "Kun" on the back of his shirt so long as he could prove that he had done so in another league (which he did in La Liga with Atletico Madrid).
Does Aguero have "Kun" on his shirt for both club and country?
The 30-year-old does have "Kun Aguero" on both his Argentina kit and his Manchester City kit, and started the tradition when he was playing for Atletico.
Which other footballers have a nickname on the back of their shirt?
Simply going by your last name is something of a forgotten tradition now, with a slew of footballers preferring to have either a nickname, their first name, or a combination of their first names and last names on the back of their shirt.
Certain footballers like Trent Alexander-Arnold and Alex Oxlade-Chamberlain, for instance, have their double-barrelled surname on their shirt while Virgil van Dijk just has "Virgil" on the back of their kit.
West Ham forward Javier Hernandez goes by "Chicharito" in his shirt, while Bryan Ruiz went by just his first name – stating that he doesn't have much of an emotional tie to the surname of his father, who left his family when he was one years old.
Brazilian footballers such as Neymar, Alisson and Marcelo – who typically go by just one name – have that singular title on the back of their jersey, and Liverpool defender Alberto Moreno has foregone with the rules entirely and has opted for an "Alberto M.".