Connected with wires; in modern usage, energetic and excited, often from consuming too much caffeine; or intensely focused and ready.
From 'wire' (from Old English 'wir') plus the suffix '-ed.' The 20th-century slang meaning of 'excited/caffeinated' developed from the sense of being 'connected' or 'turned on.'
The shift from 'wired' meaning physically connected by wires to meaning 'hyped up and energetic' is a perfect example of how technology metaphors shape how we describe emotions and states of mind.
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