The story
The ratio was first suggested in a 1974 paper by Joel H. Horovitz et al. The reason for the spelling with w is unclear.
Etymology from Wiktionary, CC BY-SA 4.0.
Horowitz index
Today it means: An assessment of lung function; the ratio of partial pressure of oxygen in blood (PaO2), and the fraction of oxygen in the inhaled air (FiO2). Full definition →