m: fanpic

I’ll write some explanation for English practice…

[Osomatsu kun → Osomatsu san]

The words “さん (san)” or “くん ,君 (kun)” are Japanese honorific suffixes.
The word which is used to both of a man and a woman.
And “san” is the word used for a superior person and an older person more.

“兄,にい,あに,あにぃ (Ni, Ani)” or “兄貴,あにき (Aniki)” = Big brother, Elder man.
The word use to a man.

“兄さん,にいさん (Nisan)” is “兄” + “さん”
Those words can be added to a person’s name.
おそ松 +  兄 + さん = Osomatsu-nisan.
Shortened to “おそ兄 (Oso ni)” .

Only Karamatsu sometime calls Osomatsu “兄貴 (Aniki)” in the animation.
(EP7 War of Imagawa-yaki scene. He said “Zurui na, aniki wa” in last chat. This means “You are not fair, bro.”)
I think this is a more manly way of saying.
He doesn’t miss acting cool.

Japanese Mafia sometime calls their superior “兄” or “兄貴” .
It seems to occur at Kyushu(九州) in particular as far as I know…

Osomatsu  (阿松 , 오소마츠, おそ松) also called “おそ兄(Oso ni)” or “長男(Chonan)”(means an eldest son) in Japanese girls.