ODM2 Variable Name Controlled Vocabulary ODM2 Working Group A vocabulary for describing the name of Variables. Holmium Holmium is a chemical element with symbol Ho and atomic number 67. Part of the lanthanide series, holmium is a rare-earth element. Holmium was discovered by Swedish chemist Per Theodor Cleve. Wikipedia https://en.wikipedia.org/wiki/Holmium Added to support Critical Zone Observatory (CZO) data use cases.