An SIV is a company of a sort that invests in assets and they issue something like asset-backed commercial paper, but it's not a real company because it only exists as an organization sponsored by some bank.

IV类似从事资产投资的公司,同时也发行类似资产担保商业票据的证券,但它不是一家真正的公司,因为它只是由某家银行建立的一个组织

耶鲁公开课 - 金融市场课程节选