means The state of being full of energy, color, or life — bright, lively, and palpably alive.

from From Latin 'vibrare,' to shake, quiver, or vibrate — the same root that gives us 'vibrate' and 'vibrant.' The idea travels from literal trembling (a plucked string, a shaken thing) to a figurative shimmer of energy: that which vibrates with life. English took 'vibrant' from the Latin present participle 'vibrans,' and 'vibrancy' is the abstract noun built atop it, naming the quality rather than the thing.