Rachitic comes from rachitis (the medical term for rickets) + -ic, from Greek rhachis ('spine, backbone'); the disease term was coined in the 17th century. The historical chain includes Ancient Greek rhachitis and Ancient Greek rhachis. Older glosses in the chain include "spine, backbone", which help explain the semantic range of the modern word. Morphologically, rachitic is best read as compound, suffixal formation, and borrowing, yielding an English adjective shaped by both form history and later usage. In current English it functions as an adjective, with the sense "affected with or relating to rickets". related forms include rickets and rachitis. The result is an English adjective whose etymology preserves the older forms while supporting the word's specialized modern meaning.