Peoples of the empire: The Arabians

History
The Classical region of Arabāya was different from modern Arabia, and included the northern part of the peninsula and part of the southern Levant.  The Arabs first appear in history living in Aram (modern Syria) thanks to that same Assyrian king who gives us earliest mention of the Persians - Šalmanasser III - when he invaded Aram and defeated a coalition of Arameans, Arabs, Israelites (sent by the fabled Ahab) and others at the Battle of Qarqar in 853 BC.

Arabia seems to have been at first an ally of the Achaemenids rather than a subject country.  Herodotus states that the Cambyses, while invading Egypt, concluded a treaty with an unnamed Arabian king who supplied his army with water while they were crossing the desert, either carried in water skins or (what Herodotus calls the least credible version) having a system of oxhide aqueducts running through the desert.

Darius would claim Arabia as one of the countries of which he was king, implying that the land later became an imperial territory or tributary kingdom.  Nonetheless, it seems to have remained largely peaceful during the Achaemenid period.

A contingent of Arabians took part in Xerxes' invasion of Greece.  They were grouped with the Ethiopians under the command of Arsames (Aršama), Xerxes' half-brother and satrap of Egypt, whose mother was Artystone.

After the fall of the Persian empire, Arabs would establish the kingdom of Arabia Nabataea or Petraea, the Greek name for which refers to the famous citadel of Petra, built inside a mountain in modern Jordan.  Nabataea remained an important regional power from the 4th century BC through AD 106, when it was annexed by Roman emperor Trajan.  Roman control over the area remained strong until the late 4th century.

Later, the Ghassanids of Yemen would move into the area and ally themselves with the Eastern Roman (Byzantine) empire against the Sassanid Persians and the Sassanids' vassals, the Lakhmids of Iraq, who were also of Yemenite origin.  Their kingdom was overthrown by early Muslims in the 7th century.  At this time, the Arabs of the peninsula began to conquer much of West Asia and North Africa, resulting in the dominance of Arabic language and (to some extent) culture from the western foothills of the Zagros to the Atlantic Ocean.

Language
One may presume that Arabs in Achaemenid times spoke Old North Arabian, the ancestor of Classical Arabic attested in scattered inscriptions from the period, although Dandamayev states that known personal names from Arabāya "do not differ from Aramaic names" and that "[i]t is still impossible to determine what language or languages these people spoke."  Old North Arabian, like its contemporaries Aramaic and Biblical Hebrew, is a Central Semitic language.

Religion
Ancient Arabians were polytheistic, although Muslims believe that some descendants of Isma'il (Ishmael) maintained the monotheistic religion of his father, Abraham; these people are known as ḥunafā' (sing. ḥanīf).  The chief god of Arabia in late pre-Islamic times was Hubal.  Al-Lat, Al-'Uzza and Manāt are said in the 9th-century Book of Idols to have been regarded as the daughters of Allah, although the earlier Nabataeans regarded Manat as Hubal's wife.

Herodotus, by contrast, asserts that in his day the Arabians believed only in Al-Lat (whom he calls Alilat) and Orotalt.  He equates these deities with Aphrodite and Dionysus respectively, but the Nabataeans would later associate Al-Lat with Athena.  Orotalt may be another name for Dushara, son of Manat and elsewhere equated with Zeus.  Herodotus states that "[t]here are no men who respect pledges more than the Arabians," and describes an elaborate ceremony calling Dionysus and Aphrodite to witness formal agreements (III.8).

Dress and arms
Arabs at the Apadana of Persepolis are shown wearing a baggy, sleeveless garment that apparently passed or fastened over the left shoulder and could be pulled up a bit and pleated in front like an Elamite robe.  Herodotus describes their clothing as "mantles girded up."  Their shoes, as near as I can tell, consist of a heel counter with either a thin strap over the instep and another just above the toes, or perhaps a long tube covering most of the foot between the toes aind instep.  The best image I can find is here, on the left, second row from the bottom.  On the table of nations at Naqš-e Rustam, the tomb of Darius the Great, the Arabian garment is shown passing over both shoulders.

Arabs had long domesticated the dromedary camel and used it for cavalry.  Herodotus says that the Arabioi "carried at their right side long bows curving backwards."  A relief from the palace of Aššurbanipal shows two Arabs riding on one camel with a saddlecloth.  They are armed with shorter D-shaped or slightly triangular bows that lack recurved tips and look more like Egyptian styles than Assyrian, and tubular quivers worn at the hip.  I have not found out anything significant about arrowhead types, but the surrounding cultures used a mix of tanged and socketed ones mostly in bronze.

The Arab at Naqš-e Rustam wears a long sword, much larger than an akinakes, pointing backward at an angle on the left hip, which appears to have a separate mushroom-shaped pommel and a long acute point.  The only possible archaeological parallel to this that I can think of is the iron sword from Persepolis.  Although its full slab tang through the grip and pommel area would make it seem likely that the pommel components were contiguous with the grip scales, it is entirely possible to attach a mushroom pommel to a slab-tanged sword.