Xiehouyu is a kind of Chinese proverb consisting of two elements: the former segment presents a novel scenario while the latter provides the rationale thereof. One would often only state the first part, expecting the listener to know the second. Compare English "an apple a day (keeps the doctor away)" or "speak of the devil (and he doth/shall appear)".
Xiēhòuyǔ is translated as "enigmatic folk simile; truncated witticism; pun" (Wenlin 2016). Puns are often involved in xiēhòuyǔ. In this case the second part is derived from the first through one meaning, but then another possible meaning of the second part is taken as the true meaning. To create examples in English, one can say "get hospitalized" to mean "be patient", or "small transactions only" to mean "no big deal". Thus a xiēhòuyǔ in one dialect can be unintelligible to a listener speaking another. Valuable linguistic data can sometimes be gleaned from ancient xiēhòuyǔ.
The origin of Xiehouyu
Xiēhòuyǔ is a special form of language created by the Chinese working people since ancient times. It is a short, funny and figurative sentence. It consists of two parts: the former part acts as a "lead", like a riddle, and the latter part plays the role of "back lining", which is like a riddle, which is quite natural. In a certain language environment, usually the first half, "rest" to the second half, can understand and guess its original meaning, so it is called "xiēhòuyǔ" ("saying with the latter part suspended").