Phrase used to exagerrate when trying to express that your experience of something predates another person's experience. The expression can be used in place of "before your were born".
An all-encompassing word/phrase which is mainly used to describe something that took place in second grade of elementary school typically with some chums. Also rarely used with a severely negative connotation and can even be derogatory when used against a small person or a dog to describe male genitalia.
Boy fine dine doe #1: yo remember when we flipped off our rabid a** teacher and Shem back flipped off the meatloaf in homeroom?
Boy slick nasty wit it #2: yooooo!! That was totally back-in-the-second-grade!!!!
Boy fine dine doe #2: OMG OMG LOML I’m such a lumpy weeeeeeen! That was definitely back-in-the-second-grade!