A History of Short Words

From the New York Times Crossword Puzzle

PSI

Sun, 24 Oct '21
Trident look-alike
Sat, 29 May '21
Inflation stat, for short
Tue, 4 May '21
... phi, chi, ___, omega
Tue, 27 Apr '21
Letter before omega
Thu, 8 Apr '21
Inflation fig.