Feeling under the weather

What is the origin of the phrase, "I'm feeling under the weather" to imply that one is feeling sick?

Previous discussion from the archives:

UNDER THE WEATHER - "Ik Marvel, a pseudonym that resulted from a misprinting of J.K. Marvel, was the pen name of American author Donald Grant Mitchell. In his 'Reveries of a Bachelor' Ik Marvel is the first to record 'under the weather,' which has been a synonym for everything from 'ill and indisposed' to 'financially embarrassed' and 'drunk,' and has even been a synonym for 'the discomfort accompanying menstruation." From Encyclopedia of Word and Phrase Origins by Robert Hendrickson (Facts on File, New York, 1997).

To be under the weather is to be unwell. This comes again from a maritime source. In the old days, when a sailor was unwell, he was sent down below to help his recovery, under the deck and away from the weather.

You're right, that explanation sounds better. Here's a similar one I found: "Under the weather. To feel ill. Originally it meant to feel seasick or to be adversely affected by bad weather. The term is correctly 'under the weather bow' which is a gloomy prospect; the weather bow is the side upon which all the rotten weather is blowing." From "Salty Dog Talk: The Nautical Origins of Everyday Expressions" by Bill Beavis and Richard G. McCloskey (Sheridan House, Dobbs Ferry, N.Y., 1995. First published in Great Britain, 1983).