Making squeaking or groaning sounds, or something that is old and starting to wear out and break down.
From the verb 'creak' (Old English 'cracettan'), which is imitative—the word sounds like the noise it describes. The '-y' suffix turns it into an adjective.
Creaky sounds are everywhere in old buildings and bodies—a haunted house has creaky floorboards, and your grandmother's knees might be creaky after climbing stairs. Language often mimics the sounds it describes.
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