What does "snuff out" mean?

Extinguish, put a sudden end to, as in Three young lives were snuffed out in that automobile accident. This usage alludes to snuff in the sense of “put out a candle by pinching the wick,” an area itself called snuff from the late 1300s on. [Mid-1800s]

Kill, murder, as in If he told the police, the gang would snuff him out. [Slang; first half of 1900s]

Also, snuff it. Die or be killed, as in He looked very ill indeed, as though he might snuff out any day, or Grandpa just snuffed it. [Slang; second half of 1800s]