remote antiquity; ancient times; the remote past
A yojijukugo (four-character idiom) used in formal or literary contexts to refer to the very distant past, often with a sense of timelessness or eternity.
This tradition has been passed down since remote antiquity.
A yojijukugo composed of 千 (thousand), 古 (old), 万 (ten thousand), and 古 (old), literally 'a thousand old, ten thousand old', emphasizing extreme age. The exact historical derivation is uncertain, but it follows a common pattern of using large numbers to express vastness of time.