Short answers, pulled from the story.
Swedish chemist Carl Gustaf Mosander discovered erbium in 1843 while analyzing a sample of yttria from the mineral gadolinite. He named the element erbia after the village of Ytterby, Sweden, where the original mineral was found.
Reasonably pure erbium metal was first produced in 1934 by Wilhelm Klemm and Heinrich Bommer. They achieved this by reducing anhydrous chloride with potassium vapor after decades of struggle to separate the element from its chemical neighbors.
Erbium-doped optical silica-glass fibers act as the active element in erbium-doped fiber amplifiers to transmit signals thousands of kilometers without electronic regeneration. The process relies on Er3+ ions that are optically pumped at around 980 nanometers and radiate light at 1550 nanometers, a wavelength with minimal loss in standard single-mode optical fibers.
Erbium lasers are used in dermatology and dentistry to cut soft tissue and remove enamel without damaging surrounding areas due to high absorption in water. The Er:YAG laser is a prime example used for ceramic cosmetic dentistry and the removal of brackets in orthodontic braces.
Naturally occurring erbium is composed of six stable isotopes including Er-162, Er-164, Er-166, Er-167, Er-168, and Er-170. Er-167 is the most abundant isotope with a natural abundance of 33.503%.
Erbium is used in nuclear technology as a neutron-absorbing control rod or as a burnable poison in nuclear fuel design to regulate the rate of fission. Humans consume 1 milligram of erbium a year on average, with the highest concentration found in the bones, kidneys, and liver.