"elongated seed vessel of beans, peas, etc.," 1680s, a word of uncertain origin; found earlier in podware "seed of legumes, seed grain" (mid-15c.), which had a parallel form codware "husked or seeded plants" (late 14c.), related to cod "husk of seeded plants," which was in Old English. In reference to a round belly from 1825; in reference to pregnancy from 1890. Meaning "detachable body of an aircraft" is from 1950.
Pod people (1956) was popularized by the movie "Invasion of the Body Snatchers," based on the 1954 novel by U.S. author Jack Finney about a plant-like alien life form that arrives on Earth as pods and are capable of replicating people.
"herd of whales or seals," 1827, American English, of unknown origin.