means A reservation is an arrangement to hold something—a table, a room, a seat—for you in advance, or, in another sense, a lingering doubt or a tract of land set aside for a specific group.

from From Latin 'reservare,' to keep back—'re-' (back) plus 'servare' (to keep, to guard, the same root that gives us 'preserve' and 'conserve'). It came through Old French 'reservation' into English meaning a thing kept in reserve. The legal and territorial senses—land 'reserved' for a particular people—and the mental sense of a held-back doubt both grew from that same core idea of holding something back rather than giving it away.