The story
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: A spurious measurement of oxygen saturation of blood, giving a false appearance of hypoxemia; it can happen via technical problems (such as a malfunctioning pulse oximeter) or even when all technical details are correct but hyperleukocytosis or thrombocytosis is present and the testing method is blood gas analysis. Full definition →
Etymology from Wiktionary, CC BY-SA 4.0.