Kahiko - Kahiko

… [Hiroshi Aramata]
[Eggs and the Japanese]
The reason why it is written as "tamago" (egg) is thought to come from its round shape, but it can also be interpreted as being because it was thought to have a soul (tama) inside it. The archaic word was "kahiko," which could be interpreted as meaning something filled with "kaheruko" or a baby inside a calcareous shell like a shell. The term has been used to refer to an unfinished product, and there is also an expression for someone in the apprenticeship stage of a craftsman called "○○'s egg."

*Some of the terminology that mentions "kahiko" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…【荒俣 宏】
【卵と日本人】
　玉子とも書くのは形が丸いところからきたと思われるが，魂（たま）の入ったものと考えたためとも解される。古語は〈カヒコ〉で，〈カヘルコ〉のつまったものとも，貝のような石灰質の殻に入った子という意味からきたとも解されよう。未成品ということから転じて，職業人の見習段階にある者を○○の卵と呼ぶ表現法もある。…

※「カヒコ」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報