Hundun (Chinese: 混沌; pinyin: Hùndùn; Wade–Giles: Hun-tun; literally: "muddled confusion") is both a "legendary faceless being" in Chinese mythology and the "primordial and central chaos" in Chinese cosmogony, comparable with the World egg.
Hundun 混沌 was semantically extended from a mythic "primordial chaos; nebulous state of the universe before heaven and earth separated" to mean "unintelligible; chaotic; messy; mentally dense; innocent as a child".
In modern Written Chinese, hùndùn "primordial chaos" is 混沌, but Chinese classic texts wrote it either 渾沌 ( in the Daoist classic Zhuangzi, etc.) or 渾敦 (Zuozhuan). Hùn "chaos; muddled; confused" is written either hùn "abundantly flowing; turbid water; torrent; mix up/in; confuse; muddle through; drift along; thoughtless; senseless" or hún (Simplified Chinese character ) "sound of running water; muddy; muddled; turbid; concealed; confused; dull; stupid; unsophisticated; whole; all over". These two are interchangeable graphic variants readable as hún 混 "muddy; dirty; filthy" (e.g., Mandarin slang húndàn 渾蛋/混蛋 "filthy egg"; bastard; scumbag") and hùn 渾 "nebulous; stupid" (hùndùn 渾沌). Dùn "dull; confused" is written either dùn "dull; confused; stupid" or dūn "thick; solid; generous; earnest; honest; sincere".
Isabelle Robinet outlines the etymological origins of hundun.
Semantically, the term hundun is related to several expressions, hardly translatable in Western languages, that indicate the void or a barren and primal immensity – for instance, hunlun 混淪, hundong 混洞, kongdong 空洞, menghong 蒙洪, or hongyuan 洪元. It is also akin to the expression "something confused and yet complete" (huncheng 混成) found in the Daode jing 25, which denotes the state prior to the formation of the world where nothing is perceptible, but which nevertheless contains a cosmic seed. Similarly, the state of hundun is likened to an egg; in this usage, the term alludes to a complete world round and closed in itself, which is a receptacle like a cavern (dong 洞) or a gourd (hu 壺or hulu 壺盧). (2007:524)