pH

Origin

Originally introduced in 1909 by S. P. L. Sørensen, using the notation p_(H⁺) for what he called the “hydrogen ion exponent” (Wasserstoffionenexponent) of a solution. He may have chosen the symbol p arbitrarily; another suggestion is that it either an abbreviation of French puissance, German Potenz, Danish potens (“power”) or English potential. The H is the international chemical symbol for the element hydrogen.