↑ "čára" in Václav Machek, Etymologický slovník jazyka českého, second edition, Academia, 1968
↑ čára in Jiří Rejzek, Český etymologický slovník, electronic version, Leda, 2007
Etymology
Probably derived from čáry(“magic”), čarovat(“to conjure”), meaning a magical line, e.g. the delineation of a magic circle.[1] Possibly connected also with Proto-Indo-European*(s)ker-(“to cut”).[2]