the study or a course of study of history before the end of the Western Roman Empire a.d. 476.
2.
information or an event of the recent past that is common knowledge or is no longer pertinent:
Last week's news is ancient history.
3.
an event, as in a person's life, that occurred in the remote past and has no practical relationship with the present:
She was my best friend in high school, but that's ancient history now.
Origin
1585-95
British Dictionary definitions for ancient history
ancient history
noun
1.
the history of the ancient world from the earliest known civilizations to the collapse of the Western Roman Empire in 476 a.d
2.
(informal) a recent event or fact sufficiently familiar to have lost its pertinence
Slang definitions & phrases for ancient history
ancient history
noun phrase
Something or someone from the past, esp an old romance: Max is ancient history
Idioms and Phrases with ancient history
ancient history
A past event, as in She's talking about her sea voyage, but that's ancient history, or And then there was his divorce, but you don't want to hear ancient history. This hyperbolic idiom transfers the field of ancient history to a much-repeated tale.