Why do so many romanian names end with "nescu" ?

I noticed a lot of romanian names end with "nescu" I was curious as to why. for example some of the most famous romanian poets names end with "nescu" such as Eminescu,Stanescu,and Paunescu. Does it have to do with what city they were born in like with italian last names ? (ie. da Vince) or does it have to do with what country you are from ? like how armenian names all end with "ian" (ie. Kim Kardahian) ... im just curious .. thanks ! :)