In Chinese, 小心 means “to be careful”. 眼 as in “眼睛” means “eyes”. So, is this word telling you “to be careful with your eyes”?
Actually No! In Chinese language, 小心眼 (xiǎo xīn yǎn) means “petty”. It is used to describe someone who is narrow-minded and mean. 心眼 literally means “mind’s eye”, but here, it refers to one’s mind. When we say “somebody’s 心眼 is small”, we actually mean “somebody is petty and cares too much about small things.”
For example, if your friend Jack held a secret grudge against you and didn’t talk to you for two years just because you said he went out of tune when he was singing, you can say “Jack 小心眼!” or “Jack 的心眼很小!” Both of the sentences mean that Jack is petty.
Besides, 小心眼 can also be used to describe someone who is stingy with money.
lǐmínɡ yìzhí bù ɡēnwǒ shuōhuà, tā búhuì háizài shēnɡ wǒde qì bɑ？
A: 李明 一直 不跟 我 说话，他 不会 还在 生 我的 气吧？
Li Ming has been avoiding talking to me. Is he still mad at me?
nǐ bié xiāshuō le, tā búshì nàzhǒnɡ xiǎoxīnyǎn de rén.
B: 你 别 瞎说了! 他 不是 那种 小心眼 的人。
Don’t say that! He is not that petty type of person.
wǒmen hé wánɡlěi yìqǐ qù chīfàn bɑ！
A: 我们 和 王磊 一起 去 吃饭 吧！
Let’s eat out with Wang Lei!
wǒ búqù. wánɡlěi fēichánɡ xiǎoxīnyǎn, měicì chīfàn, tā dōu bù tāoqián.
B: 我 不去。王磊 非常 小心眼，每次 吃饭，他 都 不 掏钱。
I am not going. Wang Lei is very stingy. He never paid the bill.