"wasting away of the body," 1650s, Modern Latin, from Greek marasmos "a wasting away, withering, decay," from marainein "to quench, weaken, wither," from PIE root *mer- "to rub away, harm" (see morbid). Maras (n.) evidently in the same sense is attested from mid-15c. Related: Marasmic.
marasmus ma·ras·mus (mə-rāz'məs)
Chronic wasting of body tissues, especially in young children, commonly due to prolonged dietary deficiency of protein and calories. Also called athrepsia.