The word 一下 is formed through the conceptual combination of its two constituent characters: 一 (yī), meaning "one", and 下 (xià), which fundamentally means "down" or "under". Their fusion creates an abstract, idiomatic unit that visually and notionally originates from the idea of a single, downward motion, like one stroke of a brush or one quick, decisive action, which then extends metaphorically to convey the general sense of a brief, quick, or tentative attempt.