Seraphim appear by name exactly once, Isaiah 6, standing above the throne in the year King Uzziah died: six wings each, two covering the face, two the feet, two for flight, crying Holy, holy, holy until the thresholds shake. One carries a live coal from the altar with tongs and touches Isaiah's mouth to purge him. The word is plural of saraph, from a root meaning to burn. Every other claim about them is later tradition.
The same consonants, saraph, name the fiery serpents that struck Israel in Numbers 21 and the flying fiery serpent of Isaiah 14 and 30. Judean seals from Isaiah's era depict serpents with two and four wings. Several scholars, Joines, Gee, Roberts, have argued Isaiah's throne attendants were winged serpent figures, upgraded to six wings for the supreme version. The burning ones may have been burning snakes first.
The claim: it is no accident that scripture's highest throne-being and its deepest villain, the serpent, the dragon, share the fiery-serpent vocabulary, seraph and nachash both carrying the sense of shining one; the tradition split one luminous serpentine archetype into loyal and rebel halves. Verdict: the philological overlap is genuine and the Ezekiel 28 cherub-serpent tangle deepens it, but identity is a leap the texts refuse to make, Isaiah's seraphim serve; Genesis's serpent seduces. Same word field, opposite vectors. Make of that what Isaiah did not.
Why does the highest angel share a root with the snake?