[anatoly]

'master' is better than 'main' because it successfully conveys the mental picture of the branch from which others are typically cloned. 'main' doesn't carry that connotation.

You could of course have branches that evolve in parallel, even without common code if you want. But what people almost always do is have one primary branch from which exact copies are made, given other names, then continue to evolve either more slowly (stable releases) or faster (speculative work). You could call that primary branch "primary" or "main" or "premier" or "trunk" and they all work, but "master" conveys that expectation very successfully, and that's why people tend to like that name.

[maverwa]

This may be because english is not my first language, or just "wrong", but for me it does not convey the that information.

Good point, how language is perceived is very subjective and personal. I can see how people like the term "master" here more than "main" because it carries more information for them. Thanks!