1) A spelling of ‘jettison’, used of goods thrown overboard from a ship in distress. The word appears to have been used in York for the compensation paid to merchants in such cases.
1457 These ar the parson that hase resseved thar jettsome, for the gudes that was kasstyn owtt of the Kattryn off Hull ... Wylliam Attkynson for xv clothys whyttis and vj dossen Kalfe skyns . More than forty individuals had payments for a wide variety of goods. The traditional meaning is clear in a later survey: 1619-21 the princes libertie of the sea ... as flotsome, jetsome, and thinges caste up and founde upon the sea shore , Pickering.