How to Change Item Names – Make Custom Language Pack: Minecraft 1.8.7
How to create a custom language pack in Minecraft Open your Minecraft folder by searching for %appdata% and pressing enter. Then open the .minecraft folder. Then open Resource packs. Alternatively, there’s an “Open Resource Pack Folder” button in your resource pack menu. Create a folder with the name of your custom language pack. Open that and create a folder called assets. Then open that and create a folder called minecraft. These should be lowercase. In the same place as your assets folder, create a new text document and paste in this text, which you’ll find in the video description.
Change the description, so you remember what your language pack does. Change LANG_COUNTRY to the name Minecraft will reference for your language file. I suggest en_ followed by something you’ll remember. Change Language Name to what you want to appear in the language menu. Change the region to your spoken language. Copy your en_name and save the document. Select Save as Type to be All Files and name it pack.mcmeta. You can delete the text document now. Inside your resource pack’s minecraft folder, create a folder called lang. Now go to your .minecraft versions folder. Open the version you’re making the language pack for. Right click the .jar file and open with an archive editing software. I recommend 7zip as it’s free to download. Link in the description. Once inside open the assets folder, then minecraft, then lang. Drag the .lang file into your lang folder. Rename the file with what we copied from our pack.metamc earlier.
Edit our .lang file with a text editor. I recommend Notepad++ because it will format everything correctly and it’s free. Download in the description. Search for the item you want to rename. Here we’ve found item.bread.name and we’re changing it to Toast. Save the file. Open your resource pack folder and enable your language pack. Now go into the language menu and you’ll see your new language available to select. There we go! Enjoy your toast. You’ll notice the old item name no longer works in the creative search menu. The game thinks it’s called Toast now!
As found on Youtube