Narrated Abu Huraira:The Prophet (ﷺ) said, "The most awful (meanest) name in Allah's sight." Sufyan said more than once, "The most awful (meanest) name in Allah's sight is (that of) a man calling himself king of kings." Sufyan said, "Somebody else (i.e. other than Abu Az-Zinad, a sub-narrator) says: What is meant by 'The king of kings' is 'Shahan Shah.,"
حَدَّثَنَا عَلِيُّ بْنُ عَبْدِ اللَّهِ، حَدَّثَنَا سُفْيَانُ، عَنْ أَبِي الزِّنَادِ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، رِوَايَةً قَالَ " أَخْنَعُ اسْمٍ عِنْدَ اللَّهِ ـ وَقَالَ سُفْيَانُ غَيْرَ مَرَّةٍ أَخْنَعُ الأَسْمَاءِ عِنْدَ اللَّهِ ـ رَجُلٌ تَسَمَّى بِمَلِكِ الأَمْلاَكِ ". قَالَ سُفْيَانُ يَقُولُ غَيْرُهُ تَفْسِيرُهُ شَاهَانْ شَاهْ.
Bukhari
Good Manners and Form (Al-Adab) • Hadith 230