Hey Marta, The expression ''so and so'' is considered to be an euphemistic way of addressing someone with an insulting term of address. (This is usually euphemistic for son of a bitch. However, it is also used for good friends, especially male to male, to show affection.) It gets the idea of ''a despised person.'' Here are some examples for you: 1) ''This lousy so-and-so tried to take me for 400 bucks.'' 2) ''You dirty so-and-so! I can't stand you!'' Hope that helps!

It's an informal and not very respectful way of referring to another person. "So and so" is often used as a substitute for a person's name when giving an example, or it can sometimes be a substitute for an insulting name. For example, if you complain to your friend that a particular shopkeeper was rude to you, your friend might agree and say "Yes, he's an old so-and-so, isn't he?". Here 'so-and-so' would mean a bad-tempered and dislikable person.

Those answering below say things I would agree with, but I'd add that "old so and so" was once such a common expression, that I'd include the "old" in the expression, as you did. This then becomes "old so and so" = disrespectful term for someone older. (Possibly used endearingly) I'd not call it a euphemism for anything stronger. It is simply not strong. . The main idea to me, is that the person has earned your disrespect through their actions.