How to keep duplicates from a string[] exclude words from a List and print them out

using System;
using System.Linq;
using System.Collections.Generic;

public class Program
{ 
    private static List<String> excludeFromText = new List<string>() {"and", "he", "the", "to", "is"};
    private static String textOnBook = "alis and joe went to the store to buy fish and salad salad is joe favorite food";


    public static void Main()
    {
        Console.WriteLine(string.Join(",", MostUsedWords(textOnBook, excludeFromText)));
    }

    public static  List<String> MostUsedWords(String textOnBook, List<String> excludeFromText)
    {
        var words = textOnBook.Split(' ');

        return words.GroupBy(z => z)
                    .GroupBy(z => z.Count())
                    .OrderByDescending(z => z.Key)
                    .First()
                    .SelectMany(z => z)
                    .Where(z => z.Length > 0)
                    .Except(excludeFromText)
                    .ToList();
     }
}