The Arabic language is one of the six official languages of the UN and the 5th most spoken language in the world; more than 400 million people speak this language, with at least 300 million being native speakers. Arabic is also the liturgical language of the 1.6 billion Muslims around the globe.
Although you may find speakers of the Arabic language across the world, they predominantly live in the Middle-east and the north African region. This is quite natural as Arabic is one of the Semitic languages: a family of languages which originated in Western Asia and North Africa. Other Semitic languages which are still spoken today include Hebrew, Aramaic, and Maltese. Of these, Arabic is the most eloquent due to its flexibility and richness in vocabulary, among other things.
Linguists and historians have attempted to trace the origin of the Arabic language. There are a few different versions as to exactly how the language came about. However, it is generally accepted that the birthplace of Arabic was in what is today Yemen and Saudi Arabia. Moreover, it came about long before the birth of Prophet Isa. There is no way of confirming how far back in time the origin of this language came from.
As for the Arabic script, its birth can be attributed to the Nabataeans whose kingdom was established in the 2nd century BC. The Nabataeans had a writing system that used a cursive Aramaic-derived alphabet. Their script would eventually transform into the Arabic alphabet.
The Arabic language was originally two languages: Old Arabic and Classical Arabic. Old Arabic traces its roots back to the southern parts of the peninsula, modern day Yemen. On the other hand, Classical Arabic was the language of the people in the central and northern parts of the Arabian peninsula. Despite being Bedouin tribes living in the harsh climate and desolate landscape of the desert, the Arabs spoke an exceedingly eloquent language. In the 6th century C.E, partly due to geopolitical shifts in the region, Classical Arabic supplanted Old Arabic as the dominant language of Arabia.
Furthermore, the Quran was revealed in the highly-developed language of the Quraysh, a merchant tribe in Mecca who trace their ancestry to the Prophet Ismail. The dialect that the Quraysh spoke was considered to be the most developed and purest form of Arabic; it was universally understood by other Arabs.
Together with the Quran, pre-Islamic Arabic poetry is considered the model for lexical semantics and Arabic grammar. On top of that, as history has shown, the spread of Islam has all but ensured the rise of Classical Arabic into prominence in the region, and its perpetual relevance in the world.