noun
some time ago; for a long time now
Often used adverbially with から to mean 'since some time ago' or 'for a while now'. The exact time span is vague and context-dependent.
See also: 前々から
前々から気になっていた店にやっと行けた。
I finally went to the shop I'd been curious about for a while.
その話は前々から聞いていました。
I've been hearing about that for some time now.
以前 is a more formal and general word for 'before' or 'previously', while 前々 is more colloquial and emphasizes a vague, ongoing period leading up to the present.
ずっと前 means 'a long time ago' and refers to a point in the distant past, whereas 前々 focuses on a period starting some time ago and often continuing to the present.
Reduplication of 前 (まえ, 'before') for emphasis, creating a sense of 'some time ago' or 'for a while now'. The exact origin is straightforward and follows a common pattern in Japanese.