decrepit (adj.)

"broken down in health, weakened, especially by age," mid-15c., from Old French decrepit (15c., Modern French décrépit), from Latin decrepitus "very old, infirm" (of old men and old animals), from de "down" (see de-) + *crepitus, past participle of crepare "to crack, break" (see raven). The literal sense of the Latin word is uncertain. Related: Decrepitly.