eō magis quod

Meaning

1. all the more (so) because: the more so because
   Reliquum erat certamen positum in virtute, qua nostri milites facile superabant, atque eo magis quod in conspectu Caesaris atque omnis exercitus res gerebatur, ut nullum paulo fortius factum latere posset;The remaining contest was one of skill, in which our soldiers easily prevailed, and all the more so because the affair was taking place in the sight of Caesar and the entire army, so that no deed, however brave, could go unnoticed.c. 52 BCE, Julius Caesar, Commentarii de bello Gallico 3.14

Origins

From eō + magis + quod.