Where does “sixtly” come from?

sixtly (English) comes from English sixt, from Middle English sixte, from Old English siexta, from Proto-Germanic sehstô — sixth.

Ancestry of “sixtly”, step by step

sixtly traces back through two separate lines of ancestry.

via English sixt

StepLanguageWordMeaning
1EnglishsixtObsolete spelling of sixth
2Middle Englishsixtesixth; A sixth; something which is sixth; A...
3Old Englishsiextasixth
4Proto-Germanicsehstôsixth

via English ly

StepLanguageWordMeaning
1EnglishlyAbbreviation of light-year
2VietnameselyAlternative spelling of li
Every word from Proto-Germanic sehstô →Every word from Old English siexta →Every word from Middle English sixte →
sixtly — Etymology, Origin & Word History | Etymology Explorer