I propose replacing
Table of Contents|Table of Contents with
Table of Contents|categories or
Table of Contents|toc, since "categories" and "toc" are system messages whose proper localized version will be shown in accordance to the language chosen in the user preferences for the rest of the interface. In English, "categories" shows "Categories", and "toc" shows "Contents".
I prefer "categories", are there other opinions? Unfortunately I don't think we have a message that displays "Table of Contents" in English, if somebody wants to help looking for better messages, the full list is in Special:AllMessages.