What does "gillyflower" mean?

Gillyflower: A kind of apple, of a roundish conical shape, purplish red color, and having a large core. [Written also gilliflower.] Clove gillflower, the clove pink. -- Marsh gillyflower, the ragged robin (Lychnis Flos-cuculi). -- Queen's, or Winter, gillyflower, damewort. -- Sea gillyflower, the thrift (Armeria vulgaris). -- Wall gillyflower, the wallflower (Cheiranthus Cheiri). -- Water gillyflower, the water violet.