I read it from a jewelry website relating to a bottle of perfume or cologne maybe? Some sort of spray? I can't seem to find a definition on google. I'm assuming French roots.
eau means water in French. Eau de cologne is a fragrant liquid (toilet water, where toilet is French for the process of washing oneself, dressing, and attending to one's appearance, or denoting articles used in the process of washing and dressing oneself) with a strong, characteristic scent, originally made in Cologne, Germany.
It should be noted that, in the US, "eau" is more than occasionally used in a pseudo-hoity-toity humorous sense, with the assumed meaning being "essence" or "odor". Someone might, eg, say "eau de skunk" or "eau de outhouse". (The use of "de" to mean "of" is not required in this sense but is usual.)