火速
huǒ sù · HSK 7
at top speed
🔥 火速 = fire (火) + speed (速): moving at fire-speed, top speed
The 火 character means fire and 速 means speed or rapid. Stacked together they push speed to its limit: doing something at top speed, full tilt, in a tearing hurry.
火 — pictograph of flames rising
火 is a pictograph showing flames rising upward from a fire, with the central stroke as the main blaze and the side strokes as sparks. The ancient oracle bone form looked even more clearly like a burning flame. It still means 'fire' today and serves as a common radical in characters related to heat, burning, or cooking.