Yellow toadflax is a member of the snapdragon family and is easily recognized by the bright yellow flowers.
Flower has a long spur, resembling a snapdragon flower.
British Dictionary definitions for snapdragon
any of several scrophulariaceous chiefly Old World plants of the genus Antirrhinum, esp A. majus, of the Mediterranean region, having spikes of showy white, yellow, pink, red, or purplish flowers Also called antirrhinum
C16: so named because the flowers, which are claimed to look like a dragon's head, have a ``mouth'' which snaps shut if squeezed open and then released
garden plant, 1570s, from snap (n.) + dragon. So called from fancied resemblance of antirrhinum flowers to a dragon's mouth. As the name of a Christmas game of plucking raisins from burning brandy and eating them alight, from 1704.