The story
Named after French mathematician Adrien-Marie Legendre (1752–1833), who introduced the symbol in 1798 in his work Essai sur la Théorie des Nombres ("Essay on the Theory of Numbers").
Etymology from Wiktionary, CC BY-SA 4.0.
Legendre symbol
Today it means: A mathematical function of an integer and a prime number, written (a/p), which indicates whether a is a quadratic residue modulo p. Full definition →