"Younger sister" in Engpsh can be translated as "younger sister". There is no specific origin for this term, it is simply a way to refer to a female sibpng who is younger than the speaker.

Example Sentences in Engpsh:

I have a younger sister who is in college.
My younger sister is very talented in dancing.
I always look up to my younger sister for her positive attitude.

Example Sentences in Chinese:

我有一个上大学的妹妹。
我的妹妹很擅长跳舞。
我总是仰望我的妹妹的积极态度。