The phrase refers to an anti-drug ad campaign that revolved around showing pictures of people in ruin with the phrase "Meth: not even once", general implication being that if you do meth even a single time it will suck you in and ruin your life.
The ad took off in the internet and was re-purposed, replacing "meth" with other things (X: not even once), generally meaning that the author of the image thinks that practicing X will lead to no good.
Someone seeing a woman's poorly-thought out tweet concerning a hot button political issue:
- Woman in politics: not even once.
by NKSedya August 6, 2019
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