The word 涂鸦 (túyā), meaning "graffiti" or "doodle", is a vivid metaphorical compound formed from two characters: 涂 (tú), which means "to smear" or "to scribble", and 鸦 (yā), which means "crow". Literally, it conjures the image of "a crow's smeared marks", evoking the messy, spontaneous, and often clumsy marks left by a bird's footprints or by someone painting without skill. Historically, the term was used self-deprecatingly by scholars to humble their own calligraphy or painting, comparing it to the unsightly scribbles of a crow. In modern usage, it has been adopted to describe the vibrant, rebellious street art of graffiti, maintaining its core essence of informal, freehand public marking.