Laudator Temporis Acti

A.Word.A.Day, Oct. 12, 2007:

stare decisis (STAYR-ee di-SY-sis) noun

The legal principle of following precedents in deciding a case, the idea that future decisions of a court should follow the example set by the prior decisions.

[Latin for "let the decision stand".]

I cannot let the translation stand. Stare decisis is not Latin for "let the decision stand," however many web pages or books say so. It means "to stand by (rest on, abide by) cases which have been decided." Stare is present infinitive of sto ("stand"). Decisis is perfect passive participle of decido ("decide"). Decisis is plural in number, and it can be argued whether its case is dative or ablative — see Lewis and Short, A Latin Dictionary, s.v. sto (II.B.1.c):

Stare in aliquā re, simply aliquā re, and post-class. also alicui rei, to stand firm, persist, persevere; to rest, abide, adhere to, continue in a thing.

The gender of decisis is probably neuter. A fuller form of the phrase is stare decisis et non quieta movere ("to stand by decided cases and not to disturb settled points"), where the neuter accusative plural quieta lends support to the idea that decisis is likewise neuter. Some, I suppose, might argue that it is feminine, modifying the understood noun rebus.

I don't know the precise origin of the phrase, that is, in what text it first occurred.