the.com/divergent series

means A series whose partial sums never approach a single finite value as you add more and more terms — it grows without bound, oscillates, or otherwise fails to converge.

from From Latin divergere, 'to turn aside, bend apart' — di- (apart) plus vergere (to bend or incline). The word entered mathematical usage as thinkers like Newton, Leibniz, and later Cauchy worked out which infinite sums actually settled toward a value and which didn't; 'diverge' was the natural word for paths of numbers that bend away from each other instead of converging on one point, borrowed from the same geometric sense used for diverging lines or opinions.