ITSI
Set to 2 different clues across 2 published puzzles, most often “Formal/informal response to "Who's there?"” — The New York Times, Thursday, 11 November 2010.
4 letters
Every clue on record, most used first
- Formal/informal response to "Who's there?"once
The New York Times — Thursday, 11 November 2010
- Odd-sounding albeit grammatical answer to "Who's there?"once
The New York Times — Thursday, 29 June 2006