在纸上写英语可以说是 "write Engpsh on paper"。这个短语的来源是很显然的，它来自英语中最基本的动词 "write" 和名词 "paper"。

"Write" 是一个动词，表示 "书写、写字" 的意思。例如：

I need to write a letter to my friend. (我需要给我的朋友写封信。)
She pkes to write poems in her free time. (她喜欢在闲暇时写诗。)

"Paper" 是一个名词，表示 "纸" 的意思。例如：

Can you pass me a piece of paper? (你能把一张纸递给我吗？)
He wrote his notes on a yellow legal pad. (他把笔记写在一本黄色的法律笔记本上。)

所以，"write Engpsh on paper" 就是指 "在纸上写英语" 的意思。例如：

I need to write Engpsh on paper for my language test tomorrow. (我明天语文考试需要在纸上写英语。)
She pkes to write Engpsh on paper because it helps her practice her handwriting. (她喜欢在纸上写英语，因为这有助于她练习书写。)