word-forming element in chemistry, used to coin element names, from Latin adjectival suffix -ium (neuter of -ius), which formed metal names in Latin (ferrum “iron,” aurum “gold,” etc.). In late 18c chemists began to pay attention to the naming of their substances with words that indicate their chemical properties. Berzelius in 1811 proposed forming all element names in Modern Latin. As the names of some recently discovered metallic elements already were in Latin form (uranium, chromium, borium, etc.), the pattern of naming metallic elements in -ium or -um was maintained (in cadmium, lithium, plutonium, etc.; helium is an anomaly).

Entries linking to -ium

helium (n.)

1868, coined from Greek hēlios “sun” (from PIE root *sawel- “the sun”), because the element was detected in the solar spectrum during the eclipse of Aug. 18, 1868, by English astronomer Sir Joseph N. Lockyer (1836-1920) and English chemist Sir Edward Frankland (1825-1899). It was not actually obtained until 1895; before then it was assumed to be an alkali metal, hence the ending in -ium.

actinium (n.)

radioactive element discovered in 1899; see actino- “pertaining to rays” + chemical suffix -ium. It emits beta rays. The name was given earlier to a supposed new element (1881).

• Harper, Douglas. “Etymology of -ium.” Online Etymology Dictionary, https://www.etymonline.com/word/-ium. Accessed 15 April, 2023.