The story
From per- + iodic acid.
Etymology from Wiktionary, CC BY-SA 4.0.
periodic acid
Today it means: HIO₄ or H₅IO₆, the oxyacids of iodine in which iodine has the highest oxidation number; H₅IO₆ is a white crystalline substance (HIO₄ is not stable), and both are strong oxidizing agents. Full definition →