Green’s Dictionary of Slang

an inferior chess-player.

1948		Chess Rev. Apr. 5/2: Immediately, spectators inquired, ‘Didn’t you see that win?’ ‘Yes,’ was the impudent reply. ‘But, with such a potzer, I draw when I will, not when he wills.’ .
1959		S. Afr. Chess-Player VII 11: That patzer Grivainis got Evans with an opening trap, but now the difference in strength begins to show [OED].
1960, 1975		Wentworth & Flexner DAS 378/1: Patzer, an inferior chess player. Although said to be from the Yiddish, there is no Yiddish, German, or Hebrew word or word combination to suggest it. Prob. from ‘patsy’ with the familiar ‘-er’ ending added.
1970		J. Hansen in Complete Brandstetter (2007) 25: ‘Do you..play chess, Mr...Brand...stetter?’ ‘I’m what’s called a potzer.’ .
1978		New Statesman 27 Oct. 556/2: He appears (or perhaps pretends) to be as tempted as the average patzer, by any old poisoned pawn, and has to have his folly explained to him.
2015		J. Colapinto Undone 375: His reaction was one of puzzled indignation — the way a grand master chess player might respond when [...] his queen is captured by a patzer.