"liable to collapse or come clattering down," 1680s, with + -y (2) + rickets, via the notion of "weak, unhealthy, feeble in the joints." The literal sense is from c. 1720 but never was common in English. Of material things, from 1799.
adjective suffix, "full of or characterized by," from Old English -ig, from Proto-Germanic *-iga- (source also of Dutch, Danish, German -ig, Gothic -egs), from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Originally added to nouns in Old English; used from 13c. with verbs, and by 15c. even with other adjectives (for example crispy).
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.
<a href="https://www.etymonline.com/word/rickety">Etymology of rickety by etymonline</a>
Harper, D. (n.d.). Etymology of rickety. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/rickety