"Long neck" is the direct translation for "长脖子" in Engpsh. The phrase does not have any specific cultural or historical origins, it is simply a physical characteristic.
Some example sentences and translations are:
"The giraffe has a long neck." (长颈鹿有一个长脖子。)
"She has a long neck, just pke a swan." (她有一个长脖子，就像天鹅一样。)
"He has a long neck, so he can reach the top shelves easily." (他有一个长脖子，所以他可以很容易地到达最上面的架子。)