The Softening Charm's only direct mention in the original novels occurs during Harry Potter's fourth year at Hogwarts School of Witchcraft and Wizardry. Prior to the First Task of the Triwizard Tournament, Professor Flitwick, the Charms master, demonstrated the charm on one of his own shoes during a class. The existence of this demonstration is revealed when Harry Potter is rigorously practicing the Summoning Charm (Accio) in his dormitory. While attempting to summon a book from across the room, he accidentally summons Professor Flitwick's softened shoe instead, which had been left behind on a desk after the lesson.
The Softening Charm appears to be a standard curriculum charm taught at Hogwarts. As it was demonstrated by Professor Flitwick in a regular Charms class, it is likely not considered particularly difficult magic. While no specific counter-spell is mentioned in the books, its effects could likely be reversed by a general Counter-Spell such as Finite Incantatem, or potentially by a Hardening Charm.
The name “Softening Charm” is purely descriptive of its effect. The incantation Spongify, which originates from the video games, is derived from the English word “sponge,” referring to the soft, porous material, combined with the common Latin-derived suffix “-ify,” meaning “to make” or “cause to become.” Thus, Spongify literally means “to make like a sponge.”
The incantation Spongify does not appear in the original seven novels and originates in the Harry Potter video games. In games such as the adaptations for Harry Potter and the Chamber of Secrets and Harry Potter and the Prisoner of Azkaban, Spongify is a commonly used spell. It is typically cast on specially marked tiles or carpets, turning them into bouncy pads that allow Harry to jump to otherwise inaccessible areas, serving as a key puzzle-solving and navigation mechanic. (video game)