chicken head

Learning languages is tough business to most people. Although much effort,most people forget what he learned. When I was studying for the examination to enter university, classic Japanese trouble me very much. After six years of learning English in school, English for examination was already easy for me.( I managed to enter university ;law)
I am embarrassed to confess the fact that I taught high school student English when I was in the university. Please don't be surprised, one of my student had American mother. I felt more dead than alive.
　As for "chicken head" , in classic Japanese it means to become a leader of small sect or organization. (To become followers in a big group is " cow's hip".) in modern Japanese, it means to forget everything only after a short time. How to use is following."He forget every things after three steps walking."Then people say "He is a chicken head".
By the way, what does "chicken head"mean in English?I didn't learn such an English phrase in the school. Someone use a phrase" chicken head girls". what does it mean?