1.
You use so-and-so instead of a word, expression, or name when you are talking generally rather than giving a specific example of a particular thing. ( INFORMAL )
It would be a case of ‘just do so-and-so and here’s your cash’...
If Mrs So-and-so was ill then Mrs So-and-so down the street would go and clean for her.
PRON
2.
People sometimes refer to another person as a so-and-so when they are annoyed with them or think that they are foolish. People often use so-and-so in order to avoid using a swear word. ( INFORMAL )
All her fault, the wicked little so-and-so.
N-COUNT [ disapproval ]