J. J. Sylvester (1851) "On a remarkable discovery in the theory of canonical forms and of hyperdeterminants," Philosophical Magazine, 4th series, 2 : 391–410; Sylvester coined the term "discriminant" on page 406.
J. J. Sylvester (1879) "On certain ternary cubic-form equations," American Journal of Mathematics, 2 : 357–393; Sylvester coins the term "totient" on page 361: "(the so-called Φ function of any number I shall here and hereafter designate as its τ function and call its Totient)"