das Schlüsselwort

The core idea of this root was:

hook, crooked piece of wood

This soon focused on the idea of closing a door by some sort of hook and the general theme of closing is still alive in many offspring today, though it’s sometimes more about a separated space.
Here’s a little (incomplete) overview – as you’ll see, many of the verbs have a translation with schließen in German.

• close, closure (“lock”… the idea of being close comes from tightness)
• disclose (“unlock”)
• enclose (“to shut in”)
• conclude (“to close with”)
• include (“to shut in”)
• seclude (“lock aside”)
• preclude (“lock in advance”)
• exclude (“lock out”)
• occlude (“lock away from”)
• clavicle (“lock like bone”)