RavenDB : Difficulty with two WHERE Query

I have a situation where I want to do a query by two fields, I thought this would be pretty simple, but it is proving a great deal more difficult than I thought.

This is a rough look at the document being queried...

class Item {
   string Id { get; set; }
   string Name { get; set; }
   Origin Origin { get; set; }
}

class Origin {
   string Id { get; set; }
   string Name { get; set; }
}

There are other fields, of course. I am just listing the relevant ones. So my Index looks like this.

public class Item__ByName : AbstractIndexCreationTask<Models.Items.Item, Item__ByName.Result> {

    public class Result {
        public string Id { get; set; }
        public string Name { get; set; }
        public string Origin { get; set; }
    }

    public Item__ByName() {
        Map = items => from item in items
                       select new Result {
                           Id = item.Id,
                           Name = item.Name,
                           Origin = item.Origin.Name
                       };

        Index(i => i.Name, FieldIndexing.Analyzed);
        Index(i => i.Origin, FieldIndexing.Analyzed);
    }
}

And then I attempt to query it like this...

var results = RavenSession
    .Query<Models.Items.Item, Indexes.Item__ByName>()
    .Where(n => n.Name == name)
    .Where(n => n.Origin.Name == origin)
    .ToList();

but it keeps telling me that "Origin_Name" is not defined. I am really confused about why it is saying this, when I've very clearly defined it.