remote; out-of-the-way; secluded
Literally 'even birds don't pass through'; a set phrase describing a place so remote or inaccessible that even birds avoid it. Often used in literary or descriptive contexts.
That village is deep in the mountains, so remote that even birds don't go there.
Explore an unexplored region so secluded that even birds avoid it.
A fixed expression composed of 鳥 (bird), も (even), 通わぬ (classical negative of 通う, 'to pass through'). The phrase paints a vivid image of a place so remote that not even birds travel there.