sēmĭ-axĭus — Lewis & Short
sēmĭ-axĭus, ii, m.axis,
I an appellation of the early Christians, derived from the manner of their martyrdom:
licet nunc sarmentitios et semiaxios appelletis, quia ad stipitem dimidii axis revincti, sarmentorum ambitu uriemur,Tert. Apol. 50.