Lewis & Short

Crĕmĕra, ae, f., a small river in Etruria, near Veii, made famous by the heroic death of the Fabii, now La Varca or Valca, Liv. 2, 49 fin.; Ov. F. 2, 205; Gell. 17, 21, 13.
Poet.: Cremerae legio, i. e. the Fabii, Juv. 2, 155.
Hence, Crĕmĕrensis, e, adj., of Cremera: dies, the day of the disastrous conflict at Cremera (with Alliensis), Tac. H. 2, 91.