ago; before the present
Literary or formal set phrase meaning 'a certain time ago' or 'in the past'. Often used in historical or narrative contexts.
A hundred years ago, a castle was built on this land.
Several decades ago, this town was a small fishing village.
A set phrase composed of 今 (now), を (object marker), and 去る (to leave, to pass). Literally 'leaving the present', it came to mean 'ago' or 'before the present'.