In Paris I noticed an ad for some fast food or other that joked, « C'est à moi. Pas touche ! »

To a learner, this idiomatic expression naturally sounds like an inversion of the expected « [Ne] touche pas ». But how did it come to be this way?

For the etymology, Wiktionnaire simply links pas and toucher and adds « siècle à préciser ». Meanwhile, the TLF, as usual not the strongest on multi-word phrases, has no entry. My Robert Micro doesn't mention it and neither does Larousse. Google results show it alive and well, though.

1. Where did this expression come from and how did it function syntactically?

What's more, my searches for the expression turned up some odd behaviour: namely, that this expression tends to be followed by à as if toucher were not transitive, suggesting that there is not much of the original toucher left qua transitive verb. « Pas touche à mes frites ! »

2. Why is this expression followed by à instead of the direct object?

Merci !

In Paris I noticed an ad for some fast food or other that joked, « C'est à moi. Pas touche ! »

To a learner, this idiomatic expression naturally sounds like an inversion of the expected « [Ne] touche pas ». But how did it come to be this way?

For the etymology, Wiktionnaire simply links pas and toucher and adds « siècle à préciser ». Meanwhile, the TLF, as usual not the strongest on multi-word phrases, has no entry. My Robert Micro doesn't mention it and neither does Larousse. Google results show it alive and well, though.

1. Where did this expression come from and how did it function syntactically?

Edit: This second part of my question turns out to be duplicated elsewhere.

What's more, my searches for the expression turned up some odd behaviour: namely, that this expression tends to be followed by à as if toucher were not transitive, suggesting that there is not much of the original toucher left qua transitive verb. « Pas touche à mes frites ! »

2. Why is this expression followed by à instead of the direct object?

Merci !