the.com/card counter

means A player who tracks which cards have already been dealt in blackjack to judge whether the remaining deck favors the player or the house, then bets accordingly.

from Not an old word at all — it's a mid-20th-century coinage tied directly to blackjack strategy theory. Mathematicians and statisticians, most famously working out 'basic strategy' and card-tracking systems in the 1950s-60s, showed that a deck with disproportionately many high cards left in it statistically favors the player, not the house. 'Counting' simply names the technique plainly: counting the ratio of high to low cards seen so far. Casinos didn't coin the term to flatter anyone — they adopted it the way police adopt the names of crimes, because it was the clearest way to describe what they were trying to ban.