En passant is today still commonplace among chess players - it means "in passing" and it "describes the capture by a pawn of an enemy pawn on the same rank and an adjacent file that has just made an initial two-square advance" [1].

Tattersal reminds me of a character in Malazan book of the fallen series of novels, I wonder if it's a reference.

[1] https://en.wikipedia.org/wiki/En_passant