岩軀の膚 is the only technique in this dictionary's two assigned styles that functions as pure defense rather than an attack — Gyomei uses it to weather a demon's assault rather than deliver one, which sets it apart structurally from every other numbered Stone or Wind form surveyed here. That defensive role is fitting for the physically strongest Hashira in the series: rather than naming a strike, Form Three names the body itself becoming rock, a passive transformation instead of an active cut.
The double body-word construction (軀 stacked with 膚, both meaning roughly "body/hide") is a small piece of intensifying redundancy — Japanese frequently pairs near-synonyms for emphasis, and here it reinforces that the hardening effect isn't localized (a stone-plated arm, say) but total: the entirety of Gyomei's physical self takes on rock's toughness. VIZ's "Stone Skin" keeps the effect legible in three syllables at the cost of that doubled emphasis, which is a reasonable trade for an attack name that needs to read instantly in a fast-paced action panel.
The corpus places it directly beside Black Blood Brambles (黒血・棘), Tanjiro's blood-based technique, on the same page — a rare panel where two characters' named techniques from entirely different fighting traditions (a Hashira's breathing style, a demon-slayer's blood ability) fire in adjacent frames of the same fight.