endearing yourself

So I was up in whistler this weekend to meet up with S and his friends but I spent most of the time traveling with my sister and her gf. What I noticed is that they called each other sweetie a lot which is an endearment that I hadn't ever heard my sister use. So I asked them how they chose this endearment - of course they don't know but my sister thinks she uses it because her gf is fond of using it (not just with the SO but with family etc). I'm terrible with endearment usage - I frankly feel really odd trying to force one out. The only one I remember someone using with me in the past was "dear". And because they used it, I guess I felt ok trying to use it as well. Anyhow, I'm curious as to if people use endearments out there and if so which ones? I don't think I hear them that often with the couples I hang out with - or else they save them for the privacy of their own home...