Upps! I must apologize for asking again. 

The point is that we actually want to keep the keys in British English so it's understandable to (almost) everyone. Do you know the tag https://wiki.osm.org/wiki/Tag:amenity%3Dluggage_locker yet? If it is also not a machine with payment option, this would be the best option from my point of view. Some hotels offer rooms for the luggage when you arrive or depart and you can't use the room yet or not anymore, that's why you can find an amenity=left_luggage on the pages of the indoor mapping (see https://wiki.osm.org/wiki/OpenStationMap#Luggage_Room)
