Short answers, pulled from the story.
A cuticle is any of a variety of tough but flexible, non-mineral outer coverings of an organism or parts of an organism that provide protection. The different structures called cuticle are non-homologous, differing in their origin, structure, function, and chemical composition.
In human anatomy, cuticle commonly refers to the thickened layer of skin surrounding fingernails and toenails, properly called the eponychium. It also names the cuticula pili, the layer of overlapping dead cells covering the hair shaft, and can serve as a synonym for the epidermis.
The main structural component of arthropod cuticle is chitin, a polysaccharide composed of N-acetylglucosamine units, together with proteins and lipids. The proteins and chitin are cross-linked, and rigidity depends on the types of proteins and the quantity of chitin.
The plant cuticle is a protective, hydrophobic, waxy covering produced by the epidermal cells of leaves, young shoots, and other aerial plant organs. It minimizes water loss, reduces pathogen entry, and acts as a permeability barrier for water and water-soluble materials.
Xerophytic plants such as cacti have very thick cuticles to survive arid climates, and plants near sea spray may have thicker cuticles to resist the toxic effects of salt. The sacred lotus resists wetting through the microscopic shape of its surface, where elevated areas reduce the contact between liquid and solid.
In mycology, cuticle refers to the outer layer of tissue of a mushroom's basidiocarp, or fruit body, and is the part removed when peeling mushrooms. The alternative term is pileipellis, and it is distinct from the inner fleshy trama and the spore-bearing hymenium.