Why curse the unborn to be without an anus? There is a common curse for the parents of the unborn &amp; their babies saying that they will be born without an anus:


  生儿子没屁眼


and it comes with variants like 生孩子没屁眼, as well.

I get the purpose of ill-wishers but why something so specific as an child without an anus? Is there something special about the anus that I am missing out on?
生仔冇屎忽 (Cantonese)
粗口之一，用作詛咒一人的後代。
狹義來說，是詛咒一人的兒子生下來會是怪胎；但現在此字眼通常用作詛咒一人，暗示他的行為會為他本人或家人帶來惡果。
現實中，生仔無屎忽的事例的確存在，被稱為閉肛症。古時有此病症者，因嬰孩不能排便，必然導致死亡，因此生仔無屎忽為非常惡毒的咀咒。現今來說，雖可施手術令到有此缺陷嬰孩通便，但因該嬰孩沒有可控制排便的肛門，即使成長，也需攜帶便袋，而渾身也會隱隱發出陣陣便臭。

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生儿子没屁眼
因为真的发生过。
大概这是中国人能想到的最恶毒的诅咒之一。在所有的身体缺陷中，可能中国人认为这是最悲惨的一种，想想如果没有肛门，那小孩还能活吗？最后肯定憋死，这句话没法追根溯源，我猜有人开始这样骂别人，被别人听到后感觉这话够劲，就纷纷开始模仿，中国人喜欢跟风你也知道，自古就这样。而且只要骂这个，被骂的人没有不怒的，作为挑衅妥妥的管用。但事实上，先天性肛门闭锁是真的在现实里存在的，可以通过手术治疗，再造一个人造肛门就可以了。

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Anus is considered 'dirty' in most cultures,  mentioning '屎忽 / 屁眼' (asshole)  is common in profanity. For example; 入你屎眼, 屎忽鬼, 食屎疴飯 in Cantonese,  屁股精 in Mandarin

Cursing someone's family is considered more hurtful than cursing that person himself or herself. Chinese believe one's evil deed will cause misfortune to his or her descendants, and son represent someone's future lineage

Cursing someone's child born without an anus is one of the most vicious curse possible. (not only someone's son will die, he will also suffer horribly before he dies )



閉肛症 or 先天性肛门闭锁 is a real birth deformity