香波 is a loanword from English 'shampoo.' The more common modern term is 洗发水 or 洗发露. 香波 is now somewhat dated but still understood. It was also historically used for champagne (香槟 is now standard for that).
memory
香 means fragrant and 波 means wave — a wave of fragrance! A vivid way to picture shampoo lathering through your hair.
