rachitic (adj.)

also rhachio-, before vowels rachi-, word-forming element meaning "spinal, pertaining to the vertebrae," from Latinized form of Greek rhakhis "spine, back," metaphorically "ridge (of a mountain), rib of a leaf," a word of uncertain origin. Compare Greek rhakhos "thorn hedge."

disease caused by vitamin D deficiency, 1630s, of uncertain origin (see note in OED). Originally a local name for the disease in Dorset and Somerset, England. Some derive it from a Dorset word, rucket "to breathe with difficulty," but the sense connection is difficult. The Modern Latin name for the disease, rachitis, comes from Greek rhakhis "spine" (see rachitic), but this was chosen by English physician Daniel Whistler (1619-1684) for resemblance to rickets.