This is spell is well obvious for making things soft and spongy. becareful of using it on a person because it would be very hard to try and turn them back normal. This Sofftening charm can make anything squishy, rubbery, and bouncey! For example a stress toy ball! its soft, squishy, rubbery, and bouncy! 

For the Etymology spongify means to "Turn into a sponge", Which of course makes sense, as objects or animals affected by the spell become sponge-like in consistency. (Down below is the sign for the spell)

Goodluck!