ebdomata
Wordlist from Comphistsem Frankfurt, Jan. 2016:
f VOC sg | f NOM sg | f ABL sg ebdomata
Latinitatis medii aevi lexicon Bohemorum (thanks to the Centre for Classical Studies at the Institute of Philosophy of the Czech Academy of Sciences (www.ics.cas.cz/en)) (2017)
ebdomata ebdomata v. hebdomada