Valetudinarian

\val-uh-too-din-AIR-ee-un; -tyoo-\ means a weak or sickly person, especially one morbidly concerned with his or her health.

I first encountered this word from one of Sherlock Holmes' stories. Though I haven't forgotten the word since I looked up its definition from a dictionary, I am including it here to share it to you. Hope you'll remember it too.

dictionary.com page link for valetudinarian