What 蛋 is referring to in "完蛋了" 完蛋了 means: Done for; ruined; finished; goose is cooked. It is the Mandarin counterpart of a Cantonese term "玩完" (game over)

I am curious about what 蛋 is referring to. Without any reference, I can only speculate


蛋 is a nickname for 'testicle'; 完蛋 simply means "f~king finished"
When a chicken stop laying egg, it is doomed and will be slaughtered soon
When an egg (蛋) is finished (完),  meaning an egg is broken, it is ruined beyond repair


Which is the correct answer? If none of the above is correct, what is the correct explanation of 蛋 in 完蛋了

I think #3 makes more sense (finish like an egg is broken)
The following text was copied from 重編國語辭典修訂本 website (http://dict.revised.moe.edu.tw/cgi-bin/cbdic/gsweb.cgi?o=dcbdic&amp;searchid=W00000002040), licensed under Creative Commons Attribution-NoDerivs 3.0 Taiwan, with the attribution to the Ministry of Education, R.O.C.



蛋


  [名]


[noun]


  1 鳥類和爬蟲類所生帶有硬殼的卵，受精之後可孵出小動物。如：「雞蛋」、「蛇蛋」、「下蛋」。


The hard-shell oval from birds or reptiles, which can produce small animals after fertilization. e.g. 雞蛋 (chicken egg), 蛇蛋 (snake egg), 下蛋 (to lay eggs).


  2 形狀像蛋的東西。如：「臉蛋兒」、「山藥蛋」。


An egg-shaped thing. e.g. 臉蛋兒 (face), 山藥蛋 (potato).


  3 斥責或罵人的話。用以比喻人或動作。如：「渾蛋」、「笨蛋」、「壞蛋」、「滾蛋」、「完蛋」、「糊塗蛋」。


A word to insult people, used as a metaphor for the action of humans. e.g. 渾蛋 (fucking asshole), 笨蛋 (stupid asshole), 壞蛋 (scoundrel asshole), 滾蛋 (Go fucking away!), 完蛋 (to be fucking finished), 糊塗蛋 (confused asshole).


  4 中國南方沿海少數民族之一。同「蜑」。如：「胡夷蛋蠻」。《宋史．卷三一．高宗本紀八》：「閏月丙午，罷廉州貢珠，縱蛋丁自便。」


A minor ethnicity in coastal South China, also written as 蜑. e.g. 胡夷蛋蠻.







蛋 in 完蛋 is definitely the third meaning: a word to insult people, used as a metaphor for the action of humans. This meaning is similar to ‘balls’ in English, the slang term of ‘testicles’.