My son says that.
I hate that term: it is inconsistent with contemporary practices and serves only to obfuscate the meaning. The chemical annotation for water can be written HOH, H(OH)–, or H2O.
Any time you have an OH– available, it is a Hydroxide. NaOH is Sodium Hydroxide. KOH is Potassium Hydroxide. The same rule applies for Mn, Fe, Co, Ni, Cu, Zn and a bunch of others!
Hydroxide is a diatomic anion.The hydroxide ion is a natural part of water, because of the self-ionization reaction: (see wiki article). To me, this nomenclature, Hydrogen Hydroxide, is more faithful to the attributes of water, as the hydroxide, OH–, is an anion and a base and the hydrogen, H+, an acid — water is simultaneously BOTH acid and base.
I prefer the term Hydrogen Hydroxide. It is neater, more consistent with practices in chemistry, and easier to understand. Of course, “water” is fine too.