The Holy part of the name comes from the fact that the Holy Furher is in fact a ordained priest, and is able to preform any and all rites of the church of the All Father. When he retired he retains this and usually becomes a high ranking bishop or even a patriarch. If a leader is especially unholy, degenerate or cruel, this may be stripped from them; However they still keep the Furher tittle. Every member of house Sternberg after Johan the Humble has not held this, with only the current leader (Hans Lebenhauer) holding the title.
Furher is simply the Altenkreis word for leader, it can mean anything from king to president. Currently it is the tittle for emperor.