The way I, and I believe most folks, read it is that certain rights cannot be “alienated” (taken away) from us.
Alienation is not "taking away"; it is any form of transfer to another party.
I have a car, and I have a house. I can sell, trade, or give them away, and they become "alienated" as far as I am concerned.
So, when we call the inherent rights with which we are "endowed" (another good technical term) by the Creator "inalienable", the meaning is that they can't be transferred to somebody else — not by conquest, nor by sale, nor even by a vote.