AssignAssetBundleNames.cs

using UnityEditor;
using System.Text.RegularExpressions;

/*
This script gives you the option to assign assets to asset bundles based on the file names.
Change the string constants below to fit your needs
*/

public class AssetBundlesUtils
{

	[MenuItem("Assets/Assign AssetBundle Names")]
	static void AssignAssetBundleNames()
	{
		const string assetFilter = "t:TextAsset";   // filter which assets should be searched (leave empty for all) 
		const string nameRegExp = @"Item\d\d";      // regexp for asset names, this one takes all files that contain Item followed by two digits

		var allTexts = AssetDatabase.FindAssets(assetFilter);
		foreach (var tex in allTexts)
		{
			var path = AssetDatabase.GUIDToAssetPath(tex);
			var name = Path.GetFileName(path);
			var m = Regex.Match(name, nameRegExp);
			if (m.Success)
			{				
				var assetSettings = AssetImporter.GetAtPath(path);
				assetSettings.assetBundleName = m.Groups[0].Value;
			}
		}
  }
  
}