It kind of looks like a little book. It's a rectangle with dashes on the side that represent the spirals of a notebook. There's a cross right on the front. Like the red cross. Or a Templar shield.
This is the Health Book icon for Windows 10
. Here we go. Optimized for 32x32 px, these are the simplest icons in the line style. Downloadable formats are PNG and SVG, among others. Icons8 icon pack is unique in providing a huge number of icons designed by the same team of four designers who create the new icons every working day in the same style and with the same quality. Same cool as the Bat Face, huh.