Archaic adverb meaning "from where" or "from what source." Anyone who uses this term seriously is either affected or was born two hundred years ago.

Saying "from whence" is redundant, as "whence," on its own, already means "from where." Anyone who says "from whence" is an arrogant moron.

A broader use of the word whence meaning when and where. In some instances it is useful to use the word ‘from’ with whence as sentence structure and meaning can be awkward without it.

Recent use by others notwithstanding, Shakespeare and J. R. R. Tolkien are two writers of note who used “from whence” in their writing.

To say once and when combined.