'Precedent' is Latin for 'going before' — a prior decision that walks ahead of all future rulings.
An earlier occurrence of something similar used as a guide; a legal decision serving as authority for future cases.
From Latin 'praecedentem,' accusative of 'praecēdēns,' the present participle of 'praecēdere' (to go before, to precede, to surpass), from 'prae-' (before, in front of) + 'cēdere' (to go, to yield, to move). 'Cēdere' derives from PIE *ked- (to go, to yield), which produced Latin 'accessus' (approach), 'concede,' 'exceed,' 'proceed,' 'recede,' 'secede,' and 'succeed.' The prefix 'prae-' comes from PIE *per- (before, forward). In classical Latin 'praecēdere' meant simply to go before in space or time