anangeon

From New Latin anangeon, from Ancient Greek ἀναγκαῖον (anankaîon), neuter of ἀναγκαῖος (anankaîos, “necessary”). The spelling of this word with -ng- is unexpected. The Latin word first appears in Jodocus Badius' annotations of Quintilian's Institutio Oratoria, printed in 1516, in which ἀναγκαῖον is glossed as Anagkeon in the text and Anangeon in the index. The latter spelling is likely an error that was introduced by the compiler of the index and copied by later authors.

来源：wiktionary