Laudator Temporis Acti

Lactantius, Divine Institutes 2.9.5-6 (tr. Mary Francis McDonald):

Of the earth itself He also made two parts contrary to and different from one another, the Orient and the Occident. Of these, the Orient is ascribed to God, because He Himself is the fount of light and illuminator of things, and because He causes us to arise to everlasting life; while the Occident is ascribed to that twisted and depraved mind, because it takes away the light, always induces darkness, and because it makes men fall and perish in sins. As the light is of the Orient, and the purpose of life is concerned with the light, so is the darkness of the Occident, and death and destruction are involved in darkness.

ipsius quoque terrae binas partes contrarias inter se diversasque constituit, orientem scilicet occidentemque. ex quibus oriens deo adcensetur, quia ipse luminis fons et inlustrator est rerum et quod oriri nos faciat ad vitam sempiternam. occidens autem conturbatae illi pravaeque menti adscribitur, quod lumen abscondat, quod tenebras semper inducat et quod homines faciat occidere atque interire peccatis. nam sicut lux orientis est, in luce autem vitae ratio versatur, sic occidentis tenebrae sunt, in tenebris autem mors et interitus continetur.

Isidore, Etymologies 13.1.4 (tr. Stephen A. Barney et al.):

The East (oriens) is named from the rising (exortus) of the sun. The West (occidens) is named because it makes the day set (occidere) and perish, for it hides the light from the world and brings on darkness.

oriens ab exortu solis est nuncupatus. occidens, quod diem faciat occidere atque interire. abscondit enim lumen mundo et tenebras superinducit.