This comes from a hitherto unknown entry in a church book.

It was the threat of state police, something hitherto unknown in Britain.

A hitherto unknown means was introduced in the electric art.

Most of the works were hitherto unknown in the west.

In fact this would simply indicate a phenomenon that was hitherto unknown.

It now remains to ask whether there is any significance in this hitherto unknown fact.

Hitherto unknown, the manuscript was analyzed in the early 21st century.

It will offer to each a degree of freedom hitherto unknown.

We are confronted by an organization in control of a hitherto unknown force.

If so, this would represent a hitherto unknown behavior for vent fish species.