Have you heard the phrase "off the reservation"?

I’ve heard it often in a military context, akin to off base, off post, off camp, off military reservation. Idk the origins of it though regarding referring to a military reservation vs Native American reservation though.

I've heard it.. would never use it.
I think of native american reservations..

I've heard of it but I've never used it. 

I've heard it. I've never used the saying. It is used to say you are going out of bounds, either a geographical restriction or outside the norms. And I believe it did initially refer to Native Americans, so I would say it is inappropriate.

I’ve heard it and it’s offensive.

Idioms by the Free Dictionary:
”1. Outside the bounds of control, propriety, or acceptance of a given group. The phrase refers to the forced relocation of Native Americans to Indian reservations in the United States. Because of this origin, the phrase is often considered offensive or inappropriate.”

Old NPR article:
”In its literal and original sense, as you would expect, the term was used in the 19th century to describe the activities of Native Americans:

"The acting commissioner of Indian affairs to-day received a telegram from Agent Roorke of the Klamath (Oregon) agency, dated July 6, in which he says: 'No Indians are off the reservation without authority. All my Indians are loyal and peaceable, and doing well." (Baltimore Sun, July 11, 1878)

www.npr.org/sections/codeswitch/2014/06/29/326690947/should-saying-someone-is-off-the-reservation-be-off-limits

I’ve never heard this phrase and I wouldn’t use it.

I"ve heard it, I would think it is offensive.

Yes, I have heard the phrase, although I dont know that I have eber used it. I will have to ask dh's native american siblings if they find it offensive. I dont get offended about things on behalf of other people.

I’ve heard the original term, but have never used it. It seems to be obviously referencing Native Americans. 

For me, “off base” is different, simply because the word “base” can be defined as something other than a military base according to the dictionary.

When I say “off base,” I don’t think of a military base (unless I am using it to literally describe something outside of a military base, such as needing to see a doctor “off base” when I usually get all my treatment on base). For me, when I usually say “off base,” base is a theoretical concept following the dictionary definition of base: “a fundamental principle or groundwork.”

I literally live right off the reservation. The expression that you gave would never ever be used up here. The man clearly doesn't know better.

To me, it’s inappropriate in the same way that saying “boatload” is inappropriate. It flippantly references situations that are typically limited to certain groups of people. It’s insensitive.

I never thought of “boatload” as inappropriate. To me it just means a lot, as in “The cruise ship brought in a boatload of people to the shops.”