The concoction was simply known as the “oil,” which was squirted under the tongue to help boost recovery after races.
mid-15c., squyrten "eject water in a jet," of uncertain origin, probably imitative. Related: Squirted; squirting.
mid-15c., originally "diarrhea," from squirt (v.). Meaning "a whipper-snapper" is from 1839.