... in analogy to "Basiswert" = "underlying (issue/asset/security)".

Compare previous English to German questions for "underlying":
http://www.proz.com/kudoz/350988
http://www.proz.com/kudoz/1549328
http://www.proz.com/kudoz/2698436

See also

https://scs.fidelity.com/webxpress/help/topics/help_definiti...
"Issuer Events
Issuer Events reflect information that pertains to Corporate bonds and Agencies/GSEs. They are designed to bring the investor's attention to key changes of the status of a particular issue or ***underlying issuer***. Examples of Issuer Events include:
Issuer upgrades and downgrades from major credit ratings agencies.
Bond placed on or removed from credit watch by major ratings agencies.
Bond has matured or been called.

Fidelity makes these events available to its customers for informational purposes only. The information has been sourced from third parties and Fidelity has made no independent evaluation of the information or its accuracy, completeness, or timeliness.

On the Secondary Corporate or Agency Bond Search Results Table, "IE" displays in the Attributes column if there are Issuer Events for an issue and would not display if there were none. Available Issuer Events can be viewed. Select "IE" or the issuer name to access Issuer Events.

Issuer Events are also available as part of Fidelity's Event Alerts services. Holders of corporate and agency bonds can elect to receive an event alert to be sent to them electronically whenever an Issuer Event is generated on one of their holdings or issuers."

http://www.reuters.com/article/idUS144765 25-Jun-2010 PRN201...
"1. Identity of the issuer or the ***underlying issuer*** of existing shares to which
voting rights are attached (ii): ..."