[DiogenesKynikos]

Because it's a widely used phrase that everyone understands.

What the "first principles" are for a layperson and a physicist are different, as is the expected level of rigor in the derivations.

[godelski]

  > that everyone understands.

We wouldn't be having this conversation if this were true

[DiogenesKynikos]

No, we're having this argument because of pedantry, not because someone doesn't understand the term "first principles."