the.com/cousin once removed

means A kinship term for someone who is your cousin but belongs to a different generation — specifically, your parent's cousin, or your cousin's child, where 'once removed' marks the one-generation gap between you.

from From 'cousin' (via Old French 'cosin,' from Latin 'consobrinus,' literally a mother's-sister's child) plus 'removed' in its old genealogical sense of 'separated by a number of generations.' The 'removed' here is the same 'remove' meaning 'a step or degree of distance,' a usage that survives chiefly in this kinship math; each 'remove' counts one generation of separation, so the language of family trees borrowed the bookkeeping vocabulary of distance to keep the branches straight.