What is Animus Manendi?

Legal Definition
The intention of remaining. To acquire a domicil, the party must have his abode in one place, with the intention of remaining there; for without such intention no new domicil can be gained, and the old will not be lost. See Domicile.
-- Bouviers Law Dictionary
Legal Definition
The intention of remaining; intention to establish a permanent residence. 1 Kent, Comm. 76. This is the point to be settled in determining the domicile or residence of a party. Id. 77.
-- Black's Law Dictionary