Linguistics
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 Daoism classic Zhuangzi, etc.) or 渾敦 (Zuozhuan). Hùn "chaos; muddled; confused" is written either hùn 混 "abundantly flowing; turbid water; torrent; mix up/in; confuse; muddle through; drift along; thoughtless; senseless" or hún 渾 (Simplified Chinese character 浑) "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 沌 "dull; confused; stupid" or dūn 敦 "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)
Most Chinese characters are written using "radicals" or "semantic elements" and "phonetic elements". Hùndùn 混沌 is written with the "water radical" 水 or 氵and phonetics of kūn 昆 and tún 屯. Hùndùn "primordial chaos" is cognate with Huntun (húntun, 餛飩, 馄饨) " wonton; dumpling soup " written with the "eat radical" 食. Note that the English loanword wonton is borrowed from the Cantonese pronunciation wan4tan1. Mair (1994:16) explains hundun and wonton, "The undifferentiated soup of primordial chaos. As it begins to differentiate, dumpling-blobs of matter coalesce. … With the evolution of human consciousness and reflectiveness, the soup would have been adopted as a suitable metaphor for chaos."
Hundun 混沌 has a graphic variant hunlun 混淪 (using lún 淪/沦 "ripples; eddying water; sink down", see the Liezi below), which etymologically connects to the mountain name Kunlun 崑崙 (differentiated with the "mountain radical" 山). Robinet (2007:525) says, "Kunlun and hundun are the same closed center of the world."
Girardot (1983:25) quotes the Chinese philologist Lo Mengci 羅夢冊 that reduplicated words like hundun "suggest cyclic movement and transformation", and speculates.
Ritually mumbling the sounds of hun-tun might, therefore, be said to have a kind on incantatory significance that both phonetically and morphologically invokes the mythological and ontological idea of the Tao as the creatio continua process of infinitely repeated moments of change and new creation.
The Shuowen Jiezi does not enter dun 沌 (which apparently lacked a pre-Han Seal script). It defines hun 混 as fengliu 豐流 "abundantly flow", hun 渾 as the sound of hunliu 混流 "abundantly-flowing flow" or "seemingly impure", dun 敦 as "anger, rage; scolding" or "who", and lun 淪 as "ripples; eddies" or "sink into; disappear".
English chaos is a better translation of hundun in the classical sense of Chaos or Khaos in Greek mythology meaning "gaping void; formless primordial space preceding creation of the universe" than in the common sense of "disorder; confusion". The latter meaning of hundun is synonymous with Chinese luàn 亂 (Simplified 乱) "chaos; disorder; upheaval; confusion; turmoil; revolt; indiscriminate; random; arbitrary". Their linguistic compound hùnluàn 混亂 (lit. "chaos-chaos") "chaos; disorder; confusion" exemplifies the "synonym compound" category in Chinese morphology.
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