whammˈy noun (informal, orig US)

1. A malevolent spell or influence cast by someone's evil eye, such a spell cast by both eyes (ie a twofold spell) being a double whammy, and a threefold spell being a triple whammy
2. Now, generally, a stunning blow, the winning punch (informal)

put the whammy on

To put the evil eye on, cast an evil spell on

wham bam thank you ma'am (vulgar sl)

Quick impersonal sexual intercourse that brings speedy gratification to the male