Eastern Arabia was historically known as Bahrain (Arabic: البحرين) until the 18th century. This region stretched from the south of Basra along the Persian Gulf coast and included the regions of Bahrain, Kuwait, Al-Hasa, Qatif, United Arab Emirates, Qatar, Southern Iraq, and Northern Oman. The entire coastal strip of Eastern Arabia was known as “Bahrain” for ten centuries.
Until very recently, the whole of Eastern Arabia, from southern Iraq to the mountains of Oman, was a place where people moved around, settled and married unconcerned by national borders. The people of Eastern Arabia shared a culture based on the sea; they are seafaring peoples.
The Arab states of the Persian Gulf are solely Eastern Arabia, the borders of the Arabic-speaking Gulf do not extend beyond Eastern Arabia. The modern-day states of Bahrain, Kuwait, Oman, Qatar and UAE are the archetypal Gulf Arab states.Saudi Arabia is often considered a Gulf Arab state although most Saudis do not live in Eastern Arabia.
In Arabic, Bahrayn is the dual form of bahr (“sea”), so al-Bahrayn means "the Two Seas". However, which two seas were originally intended remains in dispute. The term appears five times in the Qur'an, but does not refer to the modern island—originally known to the Arabs as “Awal”—but rather to the oases of al-Katif and Hadjar (modern al-Hasa). It is unclear when the term began to refer exclusively to the Awal islands, but it was probably after the 15th century. Today, Bahrain's “two seas” are instead generally taken to be the bay east and west of the coast, the seas north and south of the island, or the salt and fresh water present above and below the ground. In addition to wells, there are places in the sea north of Bahrain where fresh water bubbles up in the middle of the salt water, noted by visitors since antiquity.