Is there a common etymology for the kanji 巳 and 己 and 已?


The three characters `巳` and `己` and `已` are visually very similar, but do
they have a common etymology or any overlap in terms of semantic content?

[![visually similar
kanji](https://i.stack.imgur.com/MxqNI.jpg)](https://i.stack.imgur.com/MxqNI.jpg)

Any information would be appreciated.




  * 「巳」depicts a type of _snake_. The word that it represents ([Baxter-Sagart](https://en.wikipedia.org/wiki/Reconstructions_of_Old_Chinese#Baxter%E2%80%93Sagart_\(2014\)) [OC](https://en.wikipedia.org/wiki/Old_Chinese): **/*s-[ɢ]əʔ/** , _sixth[earthly branch](https://en.wikipedia.org/wiki/Earthly_Branches)_) is a phonetic loan.

`[商](https://en.wikipedia.org/wiki/Shang_dynasty)  
[甲](https://en.wikipedia.org/wiki/Oracle_bone_script)  
[![enter image description
here](https://i.stack.imgur.com/0O8nS.png)](https://i.stack.imgur.com/0O8nS.png)  
[甲](http://xiaoxue.iis.sinica.edu.tw/yanbian/Reference/JiaguwenReference)3915  
[合集30757](http://www.guoxuedashi.com/jgwhj/?bhfl=1&bh=30757&jgwfl=)``[西周](https://en.wikipedia.org/wiki/Western_Zhou)  
[金](https://en.wikipedia.org/wiki/Chinese_bronze_inscriptions)  
[![enter image description
here](https://i.stack.imgur.com/ljMUJ.png)](https://i.stack.imgur.com/ljMUJ.png)  
毛公鼎  
[集成2841](http://www.guoxuedashi.com/yzjwjc/?bh=2841&jgwfl=)``[戰國](https://en.wikipedia.org/wiki/Warring_States_period)・[楚](https://en.wikipedia.org/wiki/Chu_\(state\))  
[簡](https://en.wikipedia.org/wiki/Bamboo_and_wooden_slips)  
[![enter image description
here](https://i.stack.imgur.com/tmDZ6.png)](https://i.stack.imgur.com/tmDZ6.png)  
[郭・成](http://xiaoxue.iis.sinica.edu.tw/yanbian/Reference/ChuwenziReference)・36  
``[秦](https://en.wikipedia.org/wiki/Qin_dynasty)  
簡  
[![enter image description
here](https://i.stack.imgur.com/1xWeG.png)](https://i.stack.imgur.com/1xWeG.png)  
[睡](https://en.wikipedia.org/wiki/Shuihudi_Qin_bamboo_texts)・[日甲](http://xiaoxue.iis.sinica.edu.tw/yanbian/Reference/QinwenziReference)49  
``今  
[楷](https://en.wikipedia.org/wiki/Regular_script)  
[![enter image description
here](https://i.stack.imgur.com/LlP4m.png)](https://i.stack.imgur.com/LlP4m.png)  
  
`

  * 「已」( **/*ɢ(r)əʔ/** , _already_ ) was originally the same character as「巳」, and is also a phonetic loan. Much later on, the two meanings ( _sixth earthly branch_ and _already_ ) were differentiated by writing the character「已」without a fully enclosed loop at the top.

  * 「己」is graphically unrelated to the other two, and the original meaning is unclear. The earliest determined usage is for the word **/*k(r)əʔ/** , _sixth[heavenly stem](https://en.wikipedia.org/wiki/Heavenly_Stems)_. The meaning _self_ is a phonetic loan.

`商  
甲  
[![enter image description
here](https://i.stack.imgur.com/qgeUJ.png)](https://i.stack.imgur.com/qgeUJ.png)  
[燕](http://xiaoxue.iis.sinica.edu.tw/yanbian/Reference/JiaguwenReference)2  
[合集13399](http://www.guoxuedashi.com/jgwhj/?bhfl=1&bh=13399&jgwfl=)``西周  
金  
[![enter image description
here](https://i.stack.imgur.com/xacIh.png)](https://i.stack.imgur.com/xacIh.png)  
作冊大方鼎  
[集成2760](http://www.guoxuedashi.com/yzjwjc/?bh=2760&jgwfl=)``[春秋](https://en.wikipedia.org/wiki/Spring_and_Autumn_period)  
金  
[![enter image description
here](https://i.stack.imgur.com/Mj81r.png)](https://i.stack.imgur.com/Mj81r.png)  
鐘伯侵鼎  
[集成2668](http://www.guoxuedashi.com/yzjwjc/?bh=2668&jgwfl=)``戰國・楚  
簡  
[![enter image description
here](https://i.stack.imgur.com/YTiwW.png)](https://i.stack.imgur.com/YTiwW.png)  
[包2](http://xiaoxue.iis.sinica.edu.tw/yanbian/Reference/ChuwenziReference)・245  
``秦  
簡  
[![enter image description
here](https://i.stack.imgur.com/7tElu.png)](https://i.stack.imgur.com/7tElu.png)  
[睡・日乙32](http://xiaoxue.iis.sinica.edu.tw/yanbian/Reference/QinwenziReference)  
``今  
楷  
[![enter image description
here](https://i.stack.imgur.com/MwMK2.png)](https://i.stack.imgur.com/MwMK2.png)  
  
`

