the.com/regression

means A statistical method for finding the relationship between variables — and more loosely, any slide backward toward an earlier, simpler, or less developed state.

from From Latin regressus, 'a going back,' built from re- ('back') plus gradi ('to step or walk') — the same gradi that gives us 'progress' and 'gradual.' The statistical sense comes from Francis Galton's 19th-century studies of heredity, where he noticed that tall parents tend to have slightly shorter children and short parents slightly taller ones — offspring drifting back toward the average. He called this 'regression toward the mean,' and the name stuck to the whole mathematical technique, long after the biological curiosity that inspired it faded into a footnote.