According to Juliet Nicolson's book, The Perfect Summer at the turn of the 19th century and early 20th, a proper debutante always wrote thank you notes to a hostess who had held a party in her honor.These affairs were lavish and could be very expensive, so the young woman was expected to write a great deal , expressing her thanks in great detail. So much detail these letters came to be known as "Collinses" after the very long-winded Mr. Collins from Pride and Prejudice.