Lewis Short
sēmĭ-axĭus (noun M) : axis
* 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.
Charlton T. Lewis, Charles Short, A Latin Dictionary