How did 達 (~tachi) come to mean `pluralize` something?


When doing some studying, I came across the verb `達成する` which means `to
achieve/accomplish`.

When looking up 達 I realized that this is the commonly used ~達{たち} suffix
which used to pluralize something. I don't know why I've never thought the
character was a strange character for plural, as the compounds seem to have
more to do with travelling or walking than plural.

I see how it could be used in the context of 達成{たっせい} but does anyone know how
it came to mean `plural`? My guesses is that to accomplish a long journey
you'd need a large group of things or people or animals to be successful, but
that's just a shot in the dark.

### Context:

日本語

> ...平和{へいわ}が **達成{たっせい}** されたと主張{しゅちょ}します

English

> ... claim/insist to have achieved peace.




You seem to be really over-analyzing this. It is only an
[当{あ}て字{じ}](https://en.wikipedia.org/wiki/Ateji).

The plural suffix "tachi/dachi" already existed when Japanese was merely a
spoken language without a writing system. We simply assigned the kanji 「達」 to
the suffix later on.

The kanji 「達」 does not have that meaning originally, but that is the whole
point of 当て字. It is sound-based.

Definition #5 from [Wiktionary for
達](https://ja.wiktionary.org/wiki/%E9%81%94) reads:

> 5.（日本語{にほんご}）複数接尾辞{ふくすうせつびご}「たち」（または「だち」）の当{あ}て字{じ}

which is exactly what I stated above.

