Yitzchak is a lashon of simcha/laughter. Lasuach can be understood as a lashon of hachna'a, like ma tishtochachi nafshi.
Generally, when a person humbles himself and bends to the authority of another that brings sadness because it limits and controls you. But if a person humbles himself and bends to the will of HKBH that does not bring sadness. HKBH is the source of simcha - oz vechedvah bimkomo.
Yitzchak, which is simcha, comes about by lasuach, by humbling yourself and bending, basadeh, which is a reference to holiness, HKBH.