留长发，用英语可以说成 "to have long hair." 来源方面，这个说法是源自于英语中的动词 "to leave," 意思是"留下"，而 "长发" 则是由形容词 "long" 和名词 "hair" 构成。下面是一些例句：

I want to leave my hair long.

She decided to leave her hair long for the wedding.

He's been growing out his hair for months now and it's finally long enough to tie back.

中文翻译：

我想留长发。

她决定为婚礼留长发。

他经过几个月的护理，终于长到可以扎起来了。