Definition of the term Arab in historic sources
The word Arab is of uncertain meaning; when and by whom this people (or these peoples) began to be called Arabs is unknown.
The earliest sources where the term Arab appeared the first time are the Hebrew Scriptures of the post-exilic period, namely, during the rebuilding of the Temple under the Persian Empire (Nehemyah 2:19 -- 5th century b.c.e.), and is applied in a vague manner probably to some Nabatean tribes.
In the same period, also the Greek historian Herodotus mentions the Arabs, apparently in reference to the Yemenite tribes.
There are some earlier records, Akkadian and Assyrian sources that mention the "Aribi", a tribe of the desert that may be connected with the Ishmaelites, but there is not any certainty that such term has even any relationship with the word Arab.
Indeed, the term Arabia is Greek, as well as Egypt, Syria, Libya, etc. and its probable etymology may be of Semitic origin: 1) 'arabah = steppe, wilderness; 2) 'ereb = mixture of peoples.
Both terms are appropriate to them. Wherever Arabs have conquered, the lands became deserted; the Arabian peninsula itself was not so dry, and Yemen had an irrigation network that allowed the land to be fruitful before Northern Arabs invaded and subdued the Sabean kingdom.
Spain and Sicily were fertile lands in Roman times; they became dry during the Arab occupation.
Only Eretz Yisrael recovered fertility after hard work done by Jews -- the pieces of land still occupied by Arabs remain arid. The second term is also suitable to define Arabs, as they are indeed a mixture of different peoples. Arabs themselves recognize to come from two unrelated patriarchs: Qahtan (Southern Arabs) and Adnan (Northern Arabs), to be respectively identified with a Sabean and an Ishmaelite ancestor.
It seems that the name "Arabia" was applied to the whole peninsula only around the first century b.c.e., as defined by Diodorus of Sicily in his Bibliotheca Historica and by Strabo in his Geography, yet it is rather a geographic definition, not closely related with the actual ethnicity of the inhabitants, whom they declare to be of several kinds and call them by their own tribal names.
by Avraham Sándor