"Trephining" is a word in ENGLISH

A small rag or pledget introduced into the hole in the cranium made by a trephine.

A crown-saw or cylindrical saw for perforating the skull, turned, when used, like a bit or gimlet. See Trephine.

To perforate with a trephine; to trepan.

An instrument for trepanning, being an improvement on the trepan. It is a circular or cylindrical saw, with a handle …

of Trephine