from Wiktionary, Creative Commons Attribution/Share-Alike License.
- suffix Used to form the names of metal
elements, after the style of early-named elements, as well as the isotopesof hydrogen.
- suffix By extension, appended to common words to create scientific-sounding or humorous-sounding fictional substance names.
- suffix Used to indicate the setting where a given activity is carried out:
gymnasium, auditorium, stadium, colloquium, planetarium, podium, sanatorium. Words so formed often take "-a" for the plural.
from The American Heritage® Dictionary of the English Language, 4th Edition
from Wiktionary, Creative Commons Attribution/Share-Alike License
Jarrod, studying his iPhone: "But so is tin, and that doesn't end in '-ium.'"
Jarrod: "Which would mean 'aluminum' wouldn't have to end in '-ium.'"
Every other element in the periodic group it's in ends in '-ium.'
You can often tell whether a product contains quats by looking in the ingredient list for the names of chemicals ending in “-ium chloride” or “-ium bromide”—for example, cetyldimethylbenzyl-ammonium chloride or cetylpyridinium chloride.