Alaikumassalam wa rahmatullah,
Irma in the West is usually a pet form (i.e. nickname) of the German names Irmgard, Irmtraud and Ermintrude. It has the same origin as the name Emma and means “whole”, “entire”.
We can also create a Persian etymology for the name from the root Ir (which refers to the Ari people, literally meaning “noble and pure”, and is the origin of the word Iran and Aryan) and the Persian suffix ma (“female”), thus creating the meaning of “noble and pure woman”, “a woman who belongs to the Ari race”, “Iranian woman”.