Is there any connection between the choice of characters for 九 and 丸?

Question

I just learned the character 丸 and naturally noticed that it is similar to 九 with the additional 点.

Is there any interesting connection between these two characters or is it just a random coincidence ?

Answer 1

「九」 and 「丸」 are not related. As @user3306356 points out, 「丸」 is probably related to 「夗」.

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商朝
甲骨文

菁2.1
合集6057西周
金文

作冊夨令簋
集成4300戰國・晉
金文

東周左𠂤壺
集成9640
小篆

九部
說文解字今
楷書


　

「九」 depicts an arm showing the hand, a bent wrist, and elbow, indicating the original meaning elbow. This word is now written as 「肘」 (Baxter-Sagart OC: /*t-[k]<r>uʔ/).

The meaning nine (/*[k]uʔ/) for 「九」 is a phonetic loan.

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「丸」 is derived from 「夗」.

「夗」 (/*[ʔ]o[r]ʔ/) was originally a picture of an animal or person curled up in a foetal position, extended to mean twisting and turning in bed and then crooked, winding (now written 「宛」).

「夗」 or its derivatives later started being used for different senses. 「丸」 (/*[ɢ]ʷˤar/) was corrupted from 「夗」 to specifically represent the sense curl up and roll > ball, round object.

The glyph evolution and corruption process is as follows:

商朝
甲骨文

1799
殷虛文字乙
楷書


　

西周
金文

能匋尊
集成5984
隸定文字


　

西周
金文

仲義父鼎
集成2542
隸定文字


　

小篆

丸部
說文解字

晉朝
篆刻

晉烏丸率善
篆刻大字典

今
楷書


　

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References:

• 季旭昇《說文新證》
• 小學堂
• 漢語多功能字庫
• 國學大師
  • 郭沫若《甲骨文合集》
  • 中國社會科學院考古研究所《殷周金文集成》
• 中國哲學書電子化計劃
  • 宋・徐鉉等奉敕校定　漢・許慎《說文解字》

Answer 2

「丸」has more to do with「夗」than it does with「九」.

「丸」is a derivative character of「夗」.