zonk /zôNGk, zɔŋk
/ informal ▸ verb 1 [with object] hit or strike: Charley really zonked me.
2 fall or cause to fall suddenly and heavily asleep or lose consciousness: [no object] I always just zonk out and sleep straight through
[with object] I go rowing because it zonks me out.
– ORIGIN 1940s : imitative.