the.com/splitter

means A person who divides things into separate categories or parts, especially someone who emphasizes differences rather than similarities when classifying or grouping.

from Rooted in the Old English/Germanic 'splitan' meaning to cleave or break apart, 'split' has carried the sense of dividing since medieval times. The '-er' suffix simply marks the doer of the action. The word gained a specific flavor in taxonomy and scholarly debate, where 'splitters' (who multiply categories, seeing distinctions) are classically pitted against 'lumpers' (who merge them, seeing similarities) — a rivalry famously invoked by Darwin himself when grumbling about fellow naturalists' classification habits.