so-and-so
noun /ˈsəʊ ən səʊ/
  /ˈsəʊ ən səʊ/
(plural so-and-sos)
 (informal)- [usually singular] used to refer to a person, thing, etc. when you do not know their name or when you are talking in a general way
- What would you say to Mrs So-and-so who has called to complain about a noisy neighbour?
 
 - an annoying or unpleasant person. People sometimes say so-and-so to avoid using an offensive word.
- He's an ungrateful so-and-so.