English word fiery comes from Middle English fir

Detailed word origin of fiery

Dictionary entry	Language	Definition
fir	Middle English (enm)
firi	Middle English (enm)
fiery	English (eng)	Burning or glowing.. Having the colour of fire.. Hot or inflamed.. Inflammable or easily ignited.. Of or relating to fire.. Spirited or filled with emotion.. Tempestuous or emotionally volatile.