All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
The name Ash-Shaymaa’ is one of the names that the Arabs named their children with in the past.
In principle, proper names are not derived from something else, but this name was given randomly; many linguists stated this.
In any case, this name may have been derived from Ash-Shayma, which is the creation, or the nature, or from Ash-Shaamah, which is a mark or a distinguished color.
Allah knows best.