"seed covering," Middle English hol, hole, from Old English hulu "husk, pod," from Proto-Germanic *hulu- "to cover" (source also of Old High German hulla, hulsa; German Hülle, Hülse, Dutch huls), from PIE root *kel- (1) "to cover, conceal, save." Figurative use by 1831.
"body of a ship," 1550s, usually said to be identical with hull (n.1) on fancied resemblance of ship keels to open peapods. Compare Latin carina "keel of a ship," originally "shell of a nut;" Greek phaselus "light passenger ship, yacht," literally "bean pod;" French coque "hull of a ship; shell of a walnut or egg." The alternative etymology is from Middle English hoole "ship's keel" (mid-15c.), from the same source as hold (n.) and conformed to hull (n.1).
"to remove the husk of," early 15c., from hull (n.1). Related: Hulled, which can mean both "having a particular kind of hull" and "stripped of the hull."