Hygiene is the act of being clean. Washing the body to remove dirt and germs, brushing the teeth to keep them clean, shaving, using the toilet properly, and dressing correctly are some examples. Proper hygiene is often taught to children at a young age, and it becomes a habit. People who do not have good hygiene might smell bad, lose teeth, or become ill (sick).
First proven use of the word in English was in 1677s. The word hygiene comes from the French word hygiène, which is western version of Greek word ὑγιεινή (τέχνη) - hugieinē technē, meaning "(art) of health", from ὑγιεινός (hugieinos), "good for the health, healthy",  in turn from ὑγιής (hugiēs), "healthful, sound, salutary, wholesome". In ancient Greek religion, Hygeia (Ὑγίεια) was the daughter of Asclepius and represented health.