如果您想表示因为某种原因使用了生僻的英语表达方式，可以说：

"I used an obscure Engpsh expression because..."

例如：

"I used an obscure Engpsh expression because I wanted to impress my friends with my vocabulary."

或者：

"I used an obscure Engpsh expression because I came across it in a book and thought it was an interesting way to express the idea."

这种表达方式也可以用于其他语言，只需要把"Engpsh"替换成相应的语言即可。