The story
Back-formation from quantity, modeled on percentile. By surface analysis, quant(ity) + -ile.
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: One of the class of values of a variate which divides the members of a batch or sample into equal-sized subgroups of adjacent values or a probability distribution into distributions of equal probability. Full definition →
Back-formation from quantity, modeled on percentile. By surface analysis, quant(ity) + -ile.
Etymology from Wiktionary, CC BY-SA 4.0.