(PW) leave someone alone, don’t bother

She reminded me that I had to prepare for my trip out of town. I wish she would get off my back.

(free)

1. To start, as on a trip; leave.

2. a. To fire (a round of ammunition, for example): got off two shots before the deer disappeared.

b. To write and send, as a letter.

3. To escape, as from punishment or danger: got off scot-free.

4. To obtain a release or lesser penalty for: The attorney got her client off with a slap on the wrist.

5. Slang To act or speak with effrontery. Used in the imperative to express contempt or disdainful disbelief.

6. Slang To have an orgasm.

7. Slang

a. To feel great pleasure or gratification.

b. To experience euphoria, for example, as a result of taking a drug.

8. To get permission to leave one's workplace: got off early and went fishing.

(cambridge) informal

used to tell someone to stop criticizing you

Why don't you get off my back! I'm doing my best.

(hiss)

It is a very commonly used Idiom. It generally means that stop interfering or stop nudging someone in his work or anything similar. I am not sure about its origin but if you know then please let me know.
I was unable to finish my project because of my friend’s interference hence I asked him to “get of my back”.