Reham-o-Karam or raham-o-karam (shortened as Rehmo-Karam sometimes) is made of two words Rehem and Karam. Rehem is compassion while Karam is grace, favor or kindness. Frankly, both the words Rehem and Karam have nearly the same meaning and hence are used together a lot, thus making rehem-o-karam which means Compassion and Grace.
Reham-o-karam is a song sung by Vishal Dadlani and Shankar Mahadevan in Karan Johar's We Are Family.