cater-cousin

Apparently from cater +‎ cousin; further etymology uncertain. The following derivations of the first element cater have been suggested:

Stephen Skinner (1623–1667) proposed a derivation from French quatre (“four”), used in place of quatrième (“fourth”) to refer to a fourth cousin. Samuel Johnson (1709–1784) agreed, saying that the term alluded to the “ridiculousness of calling cousin or relation to so remote a degree”. The Oxford English Dictionary (“OED”) states that this “seems very unlikely”.

Instead, the OED suggests that the first element is from cater (“(obsolete) provider of food”, noun) or cater (“to provide with food”, verb), with the term originally referring to people being considered as related because they were catered for or boarded together: compare companion (literally “bread-sharer”), foster father (literally “food-father”), etc.

Anatoly Liberman (born 1937) doubts both of the above, preferring a derivation from a lost North Germanic word meaning “angled; crooked; clumsy”: compare Danish kejte (“left hand”), kejtet (“awkward, clumsy”), English cater-corner (“of or pertaining to something at a diagonal to another; (Britain dialectal, obsolete) uneven, not square, as mislaid stones or people with a limping gait”), and Swedish kaitu (“left hand”). The OED says an early Scandinavian origin “seems less convincing”.