A Wehnelt cylinder (also known as "Wehnelt cap", "grid cap" or simply "Wehnelt") is an electrode in the electron gun assembly of some thermionic devices, used for focusing and control of the electron beam.
 It is named after Arthur Rudolph Berthold Wehnelt, a German physicist, who invented it during the years 1902 and 1903.
 Wehnelt cylinders are found in the electron guns of cathode ray tubes and electron microscopes, and in other applications where a thin, well-focused electron beam is required.
Cathode rays (also called an electron beam or e-beam) are streams of electrons observed in vacuum tubes.
 If an evacuated glass tube is equipped with two electrodes and a voltage is applied, the glass behind of the positive electrode is observed to glow, due to electrons emitted from and traveling away from the cathode (the electrode connected to the negative terminal of the voltage supply).
 They were first observed in 1869 by German physicist Johann Wilhelm Hittorf, and were named in 1876 by Eugen Goldstein "Kathodenstrahlen", or cathode rays.
Julius Plücker (16 June 1801 – 22 May 1868) was a German mathematician and physicist.
 He made fundamental contributions to the field of analytical geometry and was a pioneer in the investigations of cathode rays that led eventually to the discovery of the electron.
 He also vastly extended the study of Lamé curves.
A Crookes tube (also Crookes–Hittorf tube) is an early experimental electrical discharge tube, with partial vacuum, invented by English physicist William Crookes and others around 1869-1875, in which cathode rays, streams of electrons, were discovered.
Grenz rays are part of the electromagnetic spectrum comprising low energy (ultrasoft) X-rays.
 These were first investigated by Gustav Bucky in 1923 using a cathode vacuum tube with a lithium borate glass window, which he labeled Grenz rays as he believed that the biological effects resembled those of UV light and traditional X-rays and hence were on the border between the two ("Grenz" = border in German).
 These rays are also known as Bucky rays.
Angelo Battelli (28 March 1862 – 11 December 1916) was an Italian scientist, notable for having measured temperatures and heats of fusion of non-metallic substances, metallic conductivities and thermoelectric effects in magnetic metals, and the Thomson effect.
 He investigated osmotic pressures, surface tensions, and physical properties of carbon disulfide (CS), water (HO), and alcohols, especially their vapor pressures, critical points, and densities.
 He studied X-rays and cathode rays.
 He investigated the resistance of solenoids to high-frequency alternating currents.
Eugen Goldstein (5 September 1850 – 25 December 1930) was a German physicist.
 He was an early investigator of discharge tubes, the discoverer of anode rays, and is sometimes credited with the discovery of the proton.
The history of mass spectrometry has its roots in physical and chemical studies regarding the nature of matter.
 The study of gas discharges in the mid 19th century led to the discovery of anode and cathode rays, which turned out to be positive ions and electrons. Improved capabilities in the separation of these positive ions enabled the discovery of stable isotopes of the elements.
 The first such discovery was with the element neon, which was shown by mass spectrometry to have at least two stable isotopes: Ne (neon with 10 protons and 10 neutrons) and Ne (neon with 10 protons and 12 neutrons).
 Mass spectrometers were used in the Manhattan Project for the separation of isotopes of uranium necessary to create the atomic bomb.
The history of quantum mechanics is a fundamental part of the history of modern physics.
 Quantum mechanics' history, as it interlaces with the history of quantum chemistry, began essentially with a number of different scientific discoveries: the 1838 discovery of cathode rays by Michael Faraday; the 1859–60 winter statement of the black-body radiation problem by Gustav Kirchhoff; the 1877 suggestion by Ludwig Boltzmann that the energy states of a physical system could be "discrete"; the discovery of the photoelectric effect by Heinrich Hertz in 1887; and the 1900 quantum hypothesis by Max Planck that any energy-radiating atomic system can theoretically be divided into a number of discrete "energy elements" "ε" (epsilon) such that each of these energy elements is proportional to the frequency "ν" with which each of them individually radiate energy, as defined by the following formula:
Philipp Eduard Anton von Lenard (7 June 1862 – 20 May 1947) was a German physicist and the winner of the Nobel Prize for Physics in 1905 for his research on cathode rays and the discovery of many of their properties.
 He was a nationalist and anti-Semite; as an active proponent of the Nazi ideology, he had supported Adolf Hitler in the 1920s and was an important role model for the "Deutsche Physik" movement during the Nazi period.
 Notably, he had labeled Albert Einstein's contributions to science as constituting "Jewish physics".

Question: Cathode rays were first named by which German physicist?
Answer: Eugen Goldstein