The word nwyfre is a Middle Welsh word meaning ‘sky’ or ‘vigour.’
It was usually used to refer to a windy sky.
Iolo Morgannwg, who is an interesting character worth researching, popularized its use as a ‘magical’ word. He probably misunderstood the etymology of the word, which originally had no mystical connotation, but in the sense he used it ‘nwyfre’ has taken on a life of its own in contemporary Druid circles.
The way modern Druids use the word, it now means ‘life force’ or ‘life energy.’
To a Druid, everything is alive, including rocks, trees, plants, animals, and even the Earth itself.
Everything has the potential to generate energy, and the sum total of the energy in the universe is the life force itself.
Nwyfre is in everything, it is part of everything and it can be felt on subjective if not objective levels.