diff --git a/changelog.d/downloader/3285.misc.1.rst b/changelog.d/downloader/3285.misc.1.rst
new file mode 100644
index 000000000..5861f78e4
--- /dev/null
+++ b/changelog.d/downloader/3285.misc.1.rst
@@ -0,0 +1 @@
+Fix `NameError` in :func:`redbot.cogs.downloader.downloader.Downloader._filter_incorrect_cogs_by_names()`.
diff --git a/changelog.d/downloader/3285.misc.2.rst b/changelog.d/downloader/3285.misc.2.rst
new file mode 100644
index 000000000..5b423c4e7
--- /dev/null
+++ b/changelog.d/downloader/3285.misc.2.rst
@@ -0,0 +1 @@
+Move handling of ``author`` key in ``info.json`` to :func:`redbot.cogs.downloader.json_mixins.RepoJSONMixin`.
diff --git a/redbot/cogs/downloader/downloader.py b/redbot/cogs/downloader/downloader.py
index d2f35e828..d4da0d09e 100644
--- a/redbot/cogs/downloader/downloader.py
+++ b/redbot/cogs/downloader/downloader.py
@@ -1094,7 +1094,7 @@ class Downloader(commands.Cog):
         if name_already_used:
             message += _(
                 "\nSome cogs with these names are already installed from different repos: "
-            ) + humanize_list(already_installed)
+            ) + humanize_list(name_already_used)
         correct_cogs, add_to_message = self._filter_incorrect_cogs(cogs)
         if add_to_message:
             return correct_cogs, f"{message}{add_to_message}"
diff --git a/redbot/cogs/downloader/installable.py b/redbot/cogs/downloader/installable.py
index 327d571ad..20997bb25 100644
--- a/redbot/cogs/downloader/installable.py
+++ b/redbot/cogs/downloader/installable.py
@@ -86,7 +86,6 @@ class Installable(RepoJSONMixin):
         self.repo_name = self._location.parent.stem
         self.commit = commit
 
-        self.author: Tuple[str, ...] = ()
         self.min_bot_version = red_version_info
         self.max_bot_version = red_version_info
         self.min_python_version = (3, 5, 1)
@@ -171,12 +170,6 @@ class Installable(RepoJSONMixin):
             else:
                 self._info = info
 
-        try:
-            author = tuple(info.get("author", []))
-        except ValueError:
-            author = ()
-        self.author = author
-
         try:
             min_bot_version = VersionInfo.from_str(str(info.get("min_bot_version", __version__)))
         except ValueError:
diff --git a/redbot/cogs/downloader/json_mixins.py b/redbot/cogs/downloader/json_mixins.py
index 6c8a18282..3e5b9fdc7 100644
--- a/redbot/cogs/downloader/json_mixins.py
+++ b/redbot/cogs/downloader/json_mixins.py
@@ -9,7 +9,7 @@ class RepoJSONMixin:
     def __init__(self, repo_folder: Path):
         self._repo_folder = repo_folder
 
-        self.author: Optional[Tuple[str, ...]] = None
+        self.author: Tuple[str, ...] = ()
         self.install_msg: Optional[str] = None
         self.short: Optional[str] = None
         self.description: Optional[str] = None
@@ -32,7 +32,12 @@ class RepoJSONMixin:
         else:
             self._info = info
 
-        self.author = info.get("author")
+        try:
+            author = tuple(info.get("author", []))
+        except ValueError:
+            author = ()
+        self.author = author
+
         self.install_msg = info.get("install_msg")
         self.short = info.get("short")
         self.description = info.get("description")