It's called 甚平 （じんべい）.
喝 means "scolding" or "energizing a person". It's most often used by athletes now.
There's no cultural background to this kanji used on clothes. The word has received some popularity in the last decade because it is used often in the sports section of a popular Sunday morning news program on TBS. When they show a video of a baseball player making an error or a sumo wrestler getting beaten by another of a lower rank, two commentators (ex-pro-athletes) shout "カーツ！". Some people do imitate them.
EDIT: Adding a 喝 video....