An old Item Renamer from 2011. Very flawed.

OldItemRenamer.cs

public class EnforceItemName
{
    protected void OnItemSaved(object sender, EventArgs args)
    {
        var currentItem = Sitecore.Events.SitecoreEventArgs.GetItem(args, 0);

        if (currentItem != null && currentItem.Name.Contains(" ") && (currentItem.Paths.IsContentItem || currentItem.Paths.IsMediaItem))
        {
            currentItem.Editing.BeginEdit();

            string displayName = currentItem.DisplayName;

            currentItem.Name = currentItem.Name.ToItemName().ToLower();
            currentItem.Appearance.DisplayName = displayName;
            currentItem.Editing.EndEdit();
        }
    }
}