With .pot files, translators will see the msgid values in the editor. Thus, msgid must contain the string in the source language.

If you need to preserve the key defined by your developers for each entry, you can use .po files as your source file format. You'll need to generate the .po file from the .pot file in the source language of your project. Translators will see the msgstr value in the editor, so msgstr should contain the string in the source language. The msgid can be the key of the entry.