The word you're likely thinking of is "aggredi", which is the infinitive form of the verb "aggredior".
"Aggredi" comes from the prefix "ad-" (to, towards) and the root "gradi" (to step, to walk).
Therefore, "aggredior" literally means "to step towards, to approach, to attack". This meaning evolved into the modern English word "aggression", which signifies an act of hostility or attack.