AG: Look at that, you did it!
EB: did what?
EB: you mean, this windy thing here?
One of John's powers as the Heir of Breath. Using the Windy Thing, John is able to call forth The Breeze, similar to huge gusts of wind. It allowed him to put out a fire covering almost all of LOWAS and reach the top of his echeladder at the same time. His powerful use of the Windy Thing on LOWAS alerted his Consorts and reportedly caused Typheus to stir. It briefly seemed to disperse the clouds of John's planet and free the Fireflies, but the effect was only temporary. It is likely John will have to kill his Denizen to do that.
John may have unconsciously used the Windy Thing much earlier than this, however, as the fire that he accidentally exacerbated with a Barbasol Bomb near the beginning of his journey across LOWAS was "conveniently" extinguished by a big gust of wind.
Wayward Vagabond recognizes it from his time on the battlefield, when John used it after being revived on his Quest Bed. Wayward Vagabond prompts John to do the Windy Thing for the first time via John's terminal after remembering John doing it in WV's distant past, John's near future.
The term "Windy Thing" was introduced to readers by WV through a demand of which John was not directly cognizant, but which nevertheless caused him to take up the term. John calls it that thereafter, likely introducing WV? to the term when they meet on the Battlefield. (It's possible, of course, that John never called it this to WV?, who made it up independently, in which case one can safely say the term was not coined by destiny, but by a black-carapaced vagrant.) Its actual name, if it even has one, is unknown.
The Windy Thing is also used to manipulate objects, like how John uses it to make his Dad's car fly across Skaia. The term seems to cover John's ability to create tornadoes large and powerful enough to drill to a planet's core and other wind phenomena. Tavros may have had access to this ability, but might not have been powerful enough to use it. The Salamanders consider it to be an extension of the Breeze, and it is part of John's role in their mythology.