The locale is a local region of the board suitably chosen for counting stones, intersections or points conveniently.
This definition is taken from Joseki Volume 2 Strategy, page 12. While this could be the first appearance in 2011 in printing, Robert Jasiek has used the term for several years. Usage as an unnamed concept is quite some years older. In many combinatorial game theory discussions but also in ordinary endgame calculations, implicitly the concept has been and is applied regularly by everybody. Just a name was missing.