Heathen is yet another term to describe Germanic paganism which has a similar etymology as the Latin originated word "pagan"[1]. It describes the people "of the heath"[2] — the rural folk who were the last to change their beliefs (as opposed to the city folk following the latest trends). English is unique among Germanic languages for preferring non-native vocabulary but the cognate of "heathen" is extant in every other Germanic language to describe pre-Christian belief. Among modern reconstructionists there is no consensus for a term to describe a belief system that never had a name (because prior to Christianity, it didn't need one).
That it is also a Christian pejorative term is irrelevant to the former DoD list.
That it is also a Christian pejorative term is irrelevant to the former DoD list.
[1]: https://en.wiktionary.org/wiki/paganus
[2]: https://en.wiktionary.org/wiki/heathen#English