Present participle of shut; closing something or blocking access to something.
From Old English 'scyttan' meaning to put a bar across, bolt, or fasten. Related to Old Norse 'skjóta' meaning to shoot or push quickly. The sense of closing developed from the idea of quickly moving something into a blocking position.
The connection between 'shut' and 'shoot' isn't obvious but they share the same Germanic root - both involve rapid, decisive movement. This explains why we say 'shoot the bolt' when locking a door, and why 'shutting' often implies a quick, final action rather than a gradual closing.
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