An Etymological Dictionary of Astronomy and Astrophysics

A transition metal found in zirconium ores. This silvery, ductile metal
is used in control rods for nuclear reactors and in tungsten filaments and electrodes. Symbol: Hf; Atomic mass: 178.49; Atomic number: 72; melting point 2230°C; boiling point 4602°C.

Etymology (EN): Hafnium, from N.L. Hafn(ia) “Copenhagen” + -ium. Hafnium was first observed by the French chemist Georges Urbain in 1911 in rare earth samples.
Subsequently, the Danish physicist Nils Bohr predicted hafnium’s properties using his theory of electronic configuration of the elements.