Rav and Shmuel: one said his name was Nimrod, and why was he called Amrafel? Because he cast Abraham our father into the midst of the fiery furnace. And the other said his name was Amrafel, and why was he called Nimrod? Because he made the whole world rebel against it by his kingship.
Why the King Was Called Both Nimrod and Amrafel
Yalkut Shimoni on Torah 72:3
רַב וּשְׁמוּאֵל, חַד אָמַר נִמְרוֹד שְׁמוֹ, וְלָמָּה נִקְרָא שְׁמוֹ אַמְרָפֶל, שֶׁהִפִּיל אַבְרָהָם אָבִינוּ לְתוֹךְ כִּבְשַׁן הָאֵשׁ, וְחַד אָמַר אַמְרָפֶל שְׁמוֹ, וְלָמָּה נִקְרָא שְׁמוֹ נִמְרוֹד, שֶׁהִמְרִיד כָּל הָעוֹלָם כֻּלּוֹ עָלָיו בְּמַלְכוּתוֹ.