The story
Blend of quadratic + algebraic integer. The idea of integer here is that if the coefficient of the x² term is set to 1 (i.e., if the polynomial is made monic), the other coefficients are integers.
Etymology from Wiktionary, CC BY-SA 4.0.
quadratic integer
Today it means: A number (real or complex) which is a solution to an equation of the form x²+Bx+C=0 for some integers B and C. For example 42, or 2+3i, or 1+√(-3)/2. Full definition →