Firstly I found that 「丸{まる}」 originated from 「麻呂{まろ}」:

[日本水路協会：船の名前にはなぜ「丸」が付くのか](http://www.jha.or.jp/jp/jha/charts/story/2004/08_2.html)

Then this answer said that 「麻呂{まろ}」 originated from 「おまる」:

[古代日本人の名前についている 「～麻呂」
には何か意味があるのですか？](http://detail.chiebukuro.yahoo.co.jp/qa/question_detail/q1111442251)

It started to make me feel kind of circular: from おまる to まろ to まる(again).

Then I came across this answer saying 「丸｛まる｝」 directly originated from 「おまる」:

[人名に付ける「丸」の語原について (おまる？それとも麻呂？)](http://q.hatena.ne.jp/1262937857)

Confused <@_@>
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2015-02-01T13:43:49.850
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question
etymology
Confused about the relationship between 「丸」 as in 「日本丸」 and 「麻呂」 as in 「君麻呂」
My understanding:

![enter image description here](https://i.stack.imgur.com/meoW0.png)

Giving children degrading names was widespread, and is still practiced in some
part of world, in order to deceive wicked spirits.
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