The story
From Ancient Greek ἑξακόσιοι (hexakósioi) + ἑκκαίδεκα (hekkaídeka) + English -phobia. Similar to hexakosioihexekontahexaphobia, a fear of the number of the beast; In ancient copies of the Papyrus 115 discovered in the early 2000s in Revelation 13:18 suggests 616 as the number initially recorded for the number of the beast instead of 666.
Etymology from Wiktionary, CC BY-SA 4.0.