[1875–80; hydro-1 + -lyte1]This word is first recorded in the period 1875–80. Other words that entered Englishat around the same time include: Diaspora, fan-tan, hat trick, weekend, weekenderhydro- is a combining form meaning “water,” used in the formation of compound words. Otherwords that use the affix hydro- include: hydrofoil, hydrograph, hydrometer, hydrostat, hydrotherapy