“Are you sure it’s safe?” “What are you, chicken? Buk buk bukaaaw!”
“Chicken” is used to mean “coward”. In movies, the main character often does something dangerous because someone called him chicken. Don’t try this at home!
「これは本当に安全なのかな？」「何、怖気づいた？コケコッコー！」
「卑怯者」という意味で「chicken」を使います。映画では、主人公がよく「chicken」と言われたから危険なことをしたりします。良い子はマネしないでください！
It is the same also in Japan.
What is the origin?
It is probably because people saw the chickens in their yards get startled easily. The word “chicken” has been used this way since the 14th century!