Underwriter

n. one who guarantees the sale of shares or bonds (Finance); one who provides insurance

Underwriting refers to the process that a large financial service provider (bank, insurer, investment house) uses to assess the process of providing access to their product like providing equity capital, insurance or credit to a customer. The name derives from the Lloyd's of London insurance market in London, United Kingdom. Financial bankers, who would accept some of the risk on a given venture (historically a sea voyage with associated risks of shipwreck) in exchange for a premium, would literally write their names under the risk information which was written on a Lloyd's slip created for this purpose.
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Noun
1. a banker who deals chiefly in underwriting new securities
(synonym) investment banker
(hypernym) agent, factor, broker
(hyponym) killer bee
2. an agent who sells insurance
(synonym) insurance broker, insurance agent, general agent
(hypernym) agent, factor, broker
(derivation) cover, insure, underwrite
3. a financial institution that sells insurance
(synonym) insurance company, insurance firm, insurer, insurance underwriter
(hypernym) nondepository financial institution
(derivation) cover, insure, underwrite

(n.)
One who underwrites his name to the conditions of an insurance policy, especially of a marine policy; an insurer.
  

A party that guarantees the proceeds to the firm from a security sale, thereby in effect taking ownership of the securities. Or, stated differently, a firm, usually an investment bank, that buys an issue of securities from a company and resells it to investors.