Every other Thunder Breathing form VIZ renders as plain descriptive English — "Distant Thunder," "Rice Spirit," "Rumble and Flash." Honoikazuchi no Kami alone gets left as a transliterated proper noun. That choice, translation by omission, is itself the clearest signal VIZ could give an English-only reader that this move operates on a different register from its six siblings: it isn't a description of an attack, it's somebody's name. Even the transliteration isn't fully stable — VIZ prints "HONOIKAZUCHI-NOKAMI!" in vol. 17 and "HONO-IKAZUCHI-NO KAMI!" in vol. 23, hyphenating the same proper noun two different ways within the same series, a small reminder that even official releases aren't internally consistent.
The mythology behind the name runs deep. Ho-no-Ikazuchi is one of the Yakusa no Ikazuchi (八雷神), the eight thunder gods born from Izanami's rotting body after her death in the underworld, in the Kojiki's account of Izanagi's failed rescue attempt — each god springing from a different part of her corpse, the fire-thunder god traditionally from her breast. Naming a sword technique after a specific deity born out of death and decay, rather than reaching for a generic phrase like "lightning god," is real research into Shinto cosmology on Gotouge's part, and it hands the move a genealogical, faintly blasphemous weight: the least naturally gifted swordsman in the cast names his self-made technique after a god that only exists because something else died first.
That framing matters because of who's doing the naming. Zenitsu spends the entire series being told — by his grandfather, by Kaigaku, by his own inner monologue — that knowing only the First Form is a liability in a style built around six. The story's answer isn't for him to eventually learn Forms 2 through 6; it's for him to invent a seventh, proof that mastering a single fundamental so completely it becomes one's whole identity can produce something no inherited catalogue contains. It's the direct rebuttal to Kaigaku's boast on the facing pages — "I became a demon and surpassed Thunder Breathing!!" Kaigaku surpasses the style by leaving humanity behind; Zenitsu surpasses it by staying human and going deeper into the one form he refused to abandon.
There's also a structural tell hiding in the name itself. Forms 1 through 6 are all compact two-to-four-kanji weather or sound compounds — either real words (遠雷) or readable coinages (熱界雷). 火雷神 is the only one built from a proper name lifted wholesale out of classical mythology, which puts it structurally closer to the named dances of Hinokami Kagura (Sun Breathing) than to its own numbered siblings — a naming-convention hint, well before the story confirms it outright, that Thunder Breathing and Sun Breathing share a lineage.