Early 18th century (earlier as quarteron): via French from Spanish cuarterón, from cuarto 'quarter', from Latin quartus; later assimilated to words beginning with quadri-.
Definition of quadroon in US English:
quadroon
nounkwɑˈdrunkwäˈdro͞on
offensive, dated
A person who is one-quarter black by descent.
Origin
Early 18th century (earlier as quarteron): via French from Spanish cuarterón, from cuarto ‘quarter’, from Latin quartus; later assimilated to words beginning with quadri-.