rationale of するんじゃない as informal negative imperative


I know verb-んじゃない can be used in colloquial speech as a negative imperative
(e.g. するんじゃない) in lieu of verb-な (するな), but why exactly does it function that
way? That is, what is the rationale/etymology behind v-んじゃない being a negative
imperative?




Obviously it's not grammatical imperative, but the construction _functions_ as
order when used by somebody's betters (senior, superior etc.) to strongly
admonish them. If I can ignore context, "You don't want to do --!" could be a
way of translation.

  * V(する)-んだ！ (more pompously V(する)-のだ！): affirmative command
  * V(する)-んじゃない！ (V(する)-のではない！, V(する)-でない！): negative command

Incidentally, the dictionary form is also employed as command, with colloquial
but very overbearing tone.

  * V(する)！: affirmative
  * V(し)-ない！: negative




Obviously it's not grammatical imperative, but the construction _functions_ as
order when used by somebody's betters (senior, superior etc.) to strongly
admonish them. If I can ignore context, "You don't want to do --!" could be a
way of translation.

  * V(する)-んだ！ (more pompously V(する)-のだ！): affirmative command
  * V(する)-んじゃない！ (V(する)-のではない！, V(する)-でない！): negative command

Incidentally, the dictionary form is also employed as command, with colloquial
but very overbearing tone.

  * V(する)！: affirmative
  * V(し)-ない！: negative

