This is the 11th most frequent Tamil word.
இர
Be / Exist.
Here, 'இரு' is a verb that expresses the state of doing something.
நான் காத்திருக்கிறேன்
I am waiting.
Here, 'இரு' is used as part of a compound word 'இருந்தாலும்' to indicate a shift in context.
இருந்தாலும், நாம் முயற்சி செய்ய வேண்டும்.
Nevertheless, we must try.
In this context, 'இரு' describes the physical state of standing.