All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
Ilyaas and Ilyaaseen are two names for this Prophet. Al-Qurtubi said, “What is meant is Ilyaas and it is on him that Allaah sent peace (i.e. in the verse which means, 'Peace be upon Ilyaaseen' [Quran 37:130]), but it is a non-Arabic name. The Arabs confuse these non-Arabic names and they frequently change them. Ibn Jinni said, 'The Arabs greatly alter the pronunciation of non-Arabic names; Yaaseen, Ilyaas and Ilyaaseen are the same person...'”
Besides, the Tafseer of At-Tabari, reads, “The reciters of the Quran differed in reciting the saying of Allaah: {Peace be upon Ilyaaseen} [Quran 37:130] The majority of the reciters of Makkah, Basrah, and Koofah pronounced it Ilyaaseen. Some of them said that this was the name of Ilyaas and that he was called by two names: Ilyaas and Ilyaaseen; like Ibraaheem and Ibraahaam…”
Allaah knows best.