Orthanc is the black tower of Isengard that houses one of the palantíri. A palantír is a spherical stone whose name literally means “One that Sees from Afar”. When one looks into a palantír, one can communicate with other such stones and anyone who might be looking into them. This is quite similar to the Orthanc server, which is designed for a simple, transparent, programmatic access to medical images in the entire hospital DICOM topology.
“Orthanc” also contains the trigram “RTH”, standing for Radiotherapy. This is a reference to the fact that Orthanc originates from research on cancer that is carried on at the University Hospital of Liège, in the Department of medical physics.