A History of Short Words

From the New York Times Crossword Puzzle

ITSME

Sun, 17 Apr '22
Response to "Who's there?"
Fri, 4 Feb '22
Part of a classic breakup line
Sat, 6 Nov '21
Response at the door
Sun, 9 May '21
Apologetic remark during a breakup
Sun, 11 Apr '21
"Who's there?" response
Wed, 20 Jan '21
Self proclamation?