Shabnam is a highly used word in Bollywood songs. It's an Urdu word which means Dew drops. In Hindi, it's 'os'.
Shabnam comes from the root word Shab which means Night and Nam, which comes from nami, that is moisture, hence making Shabnam, the night-moisture, or simply dew.
A variant of Shabnam which is used is Shabnami, which is 'like dew.'