The notion that filenames preceded by a . should be hidden is the result of a software bug in the early days of Unix. When the special . and .. directory entries were added to the filesystem, it was decided that the ls command should not display them. However, the program was mistakenly written to exclude any file whose name started with a . character, rather than the exact names . or ...
https://unix.stackexchange.com/questions/88875/why-are-filenames-that-start-with-a-dot-hidden-can-i-hide-files-without-using-a
https://unix.stackexchange.com/questions/88875/why-are-filenames-that-start-with-a-dot-hidden-can-i-hide-files-without-using-a