Trivial name for example, hydrogen ("water-producing"), oxygen ("acid-producing"), nitrogen ("soda-producing"), bromine ("stink"), and argon ("no reaction") were based on Greek roots, while the names of iodine and chlorine were derived from the Greek words for their characteristic colors. Indium, rubidium, and thallium were similarly named for the colors of particular lines in their emission spectra. Iridium, which forms compounds of many different colors, takes its name from "iris", the Latin for "rainbow". The noble gases have all been named for their origin or properties. Helium comes from the Greek "helios", meaning "sun" because it was first detected as a line in the
Systematic element name for 4). There are two elision rules designed to prevent odd-looking names. The suffix "-ium" overrides traditional chemical suffix rules; thus elements 117 and 118 were "ununseptium" and "ununoctium", not "ununseptine" and "ununocton". This does not apply to the final trivial names these elements receive once confirmed; thus element 117 and 118 are now "tennessine" and "oganesson". For these trivial names, all elements receive the suffix "-ium", except those in group 17 which receive "-ine" (like the halogens) and those in group 18 which receive "-on" (like the noble gases). The systematic symbol is formed by taking the first letter