From Halopedia, the Halo wiki
CAA Irbid was a colony ship of the Unified Earth Government's Colonial Administration Authority. The personnel of the ship claimed to have colonized the planet of Tribute in the Epsilon Eridani system on July 24, 2364. However, the UEG officially recognizes CAA Casbah's colonization efforts on August 8, 2364 to have been the official date of Tribute's colonization. Tribute's city of Irbid was named after CAA Irbid.
The ship may be named for the city of Irbid in Jordan.