hund-nigontigoþa [OE]
nyntithe [MI]
nintieth [ME]
nyntieþ
https://www.etymonline.com/word/ninetieth#etymonline_v_45307
https://www.merriam-webster.com/dictionary/ninetieth
https://quod.lib.umich.edu/m/middle-english-dictionary/dictionary/MED29555
https://bosworthtoller.com/53359