blind carbon copy

noun
  1. a duplicate of anything written or typed, or a copy of an email or other electronic document, that is sent to someone whose name is not visible to the primary addressee. Abbreviation: bcc

Origin of blind carbon copy

with reference to the former use of carbon paper to make copies, now replaced by electronic or photocopied documents
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018