letter of comfort

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun finance A type of letter popular in the 1980s addressed to a lender giving some type of reassurance about the position of a borrower (or prospective borrower). Such a letter is written by someone substantial such as a parent company or major shareholder, but is not a guarantee and usually not even a legally enforceable undertaking (making it in practice almost worthless, yet lenders at various times have found such letters comforting).