“They call me Kyon, but I don’t like it.” Kyon says.
Why do they call him Kyon and why doesn’t he like it?
Kyon was a childhood nickname. His little sister kept using it, even though he went by his real name at school. His friends overheard her and started doing it to be funny.
He’s not annoyed because it means anything bad. He’s annoyed because it was a family nickname from when he was a little kid.
Say you’re a teenager named “Scott”. But your little sister has called you “Toot” since you were eight years old. Your friends overhear her and now everyone at school calls you “Toot”. That’s what it’s like.
Two funny things about Kyon:
(1) Kyon is the narrator. He complains about his nickname, but he never tells you what his real name is. (To be fair, the one time when he should have given it, when everyone in class is introducing themselves on the first day of high school, that part gets cut out of his speech, perhaps to make room for the next student’s self-introduction, that of Suzumiya Haruhi).
(2) The person who started it all, Kyon’s little sister, has even less of a name: in Japanese she is just “Kyon no imouto” – literally, Kyon’s little sister – and has no name or nickname.
Manga and anime, particualrly comedically-slanted ones, do this a lot. I remember an episode of Urusei Yatsura where Ataru Moroboshi’s mother (whose name is never revealed) actually said “I am Ataru Moroboshi’s mother” with a completely straight face. The racing mangas are full of minor characters who have no name or only a family name…Tsukamoto, the Two Guys From Tokyo, the Evo 5 and 6 drivers.
In Kyon’s case, I think this was done expressly to make him generic and malleable. Names carry weight in Japan, particularly family names, and the last thing Kyon needs is to be pigeonholed. Kyon is a cynical straight man, the “Adam” to Haruhi’s “God”, which makes his adventures and discoveries all the more intriguing. Note that we also don’t know anything about his parents, his early life, his hobbies and interests, his future plans, etc., all common methods of making a charater as open-ended as humanly possible.
As for his sister, maybe it’s just me, but I always end up calling her “Lady Kyon”. 