Meaning:
Literally, “毛” means “hairy,” and “孩子” means “child.” This Chinese term has been in use for a long time, referring to “children or minors,” and sometimes “young people” with a derogative connotation of “being ignorant and inexperienced.” However, more and more people today use it in the literal sense to refer to their pets, whom they treat dotingly like their own kids.
Example:
A: 你有件快递，放你办公桌上了。你又网购了什么好东西？
Nǐ yǒu jiàn kuàidì, fang nǐ bàngōngzhuō shàng le。Nǐ yòu wǎnggòu le shénme hǎodōngxi?
The courier has got a parcel for you and it’s sitting on your desk. What’s the fancy stuff you purchased online this time?
B: 是个宠物自动饮水机。最近我给毛孩子买了太多东西了。
Shì ge chǒngwù zìdòng yǐnshuǐjī。Zuìjìn wǒ gěi máoháizi mǎi le tàiduō dōngxi le。
It’s an automatic water dispenser for pets. I’ve bought too many things for my pet lately.