Talking about horses...
This is a word used by Japanese people colloquially to insult someone.
I found the Chinese characters (Kanji) that make up this word interesting.
Meaning: fool, stupid, idiot
Kanji: "horse" and "deer"
I've heard that this is so because the word describes someone who is so stupid that he can't even perceive the difference between a horse and a deer...
You have to have a special talent for that, or be like, very very drunk :P