Where does it originate from?
In ancient China, most houses are oriented north and south. There is a drawing room in the middle with two seats placed to the east and to the west. The host usually seats the guest at the western seat before taking the other seat to the east. Also, it is often customary for the guest to walk on the west side of the road and the host to walk along side the guests on the eastern side of the road. Thus, the host has become known as the 东道主(dōngdàozhǔ), or 东(dōng) for short. Naturally, 做主人(zuò zhǔrén), or 'to be a host' becomes 做东(zuòdōng).
What does it mean?
The phrase 做东(zuòdōng) is widely used to describe that someone is acting as a host, but it literally means 'to be the east.' 做(zuò) means'to do'or 'to act as;' 东 means 'the cardinal direction east,' but in the phrase 做东(zuòdōng), it means host. Usually, the phrase 做东(zuòdōng) is used when one invites others or treats them to dinner.
How to use it?
Examples:
今天我做东，明天轮到你了！ Jīntiān wǒ zuòdōng, míngtiān lún dào nǐ le!
Today, I'll invite you to dinner and tomorrow it'll be your turn!
今晚我做东，大家玩个尽兴。 Jīnwǎn wǒ zuòdōng, dàjiā wán gè jìnxìng.
It is my treat tonight, please enjoy yourselves.
吹牛(chuīniú) Brag and Boast
Origin and meaning
It is said that the phrase 吹牛(chuīniú) comes from the butcher shop. In some places, when the butcher butchers pigs and sheep, he will cut a small slit on the pigs' or sheep's leg near the hoof and inflate them by blowing through the slit until the whole body expands after the blood has been completely drained, thus making the skin very easy to peel. This is called inflating pigs or sheep. If this is done to a cow, it would be called 吹牛(chuīniú), which literally means to inflate a cow. However, because a cow has such a huge body, it is very difficult for ordinary people to inflate it by themselves. Thus, anyone who claims that he can inflate a cow is completely bragging or boasting. 吹(chuī) in the phrase 吹牛(chuīniú) means to blow and 牛(niú) means cow, but 吹牛(chuīniú) is widely used to describe people who are bragging and boasting.
Usage of the phrase
Examples:
别听他的，他很爱吹牛！ Bié tīng tā de, tā hěn ài chuīniú!
Don't believe him, he loves to brag.
他是个吹牛的能手，每天都说一些让人无法相信的事！ Tā shì gè chuīniú de néngshǒu, měitiān dōu shuō yīxiē ràng rén wúfǎ xiānɡxìn de shì!
He is good at bragging and often says some very unbelievable things.
