Allah and El both mean "The God" in Arabic and Hebrew, respectively. They still had a pantheon of minor gods and goddesses.
Zoroastrians were the first monotheistic religion group and worshipped Ahura Mazda as their chief god, but even they worshipped minor gods and spirits.
‘Judeo-Christian/Islamic’ monotheism was first practiced by Cushites. The concept of a single god associated with the sky and evil represented by spirits.
These ideas were from the Nile valley but Cushites were first to adopt it according to Ehret.