CeDe - Acronym, Initialism or Portmanteau?

The Depository Trust Company provides depository and book-entry services and operates a securities settlement system.  The DTC's nominee is CeDe & Co. which is generally pronounced as the letters "C" and "D".  The name is an abbreviation of "certificate depository".  See S.E.C. Release No. 34-76743, p. 31, n. 87 (Dec. 22, 2015). 

Some might be inclined to describe CeDe an acronym.  It would be an acronym, if it were pronounced as a word.  The J.O.B.S. (Jumpstart Our Business Startups) Act is an example of an acronym.  The word "acronym" was coined based on two Greek words -ἄκρος (meaning the highest point) and ὄνομα (meaning name).

CeDe is an initialism because it is pronounced by saying each letter.  Other examples of initialisms that are not acronyms include S.E.C. and D.B.O.  

Brexit might appear to fall within the category of acronym, but it is a portmanteau word, a fusing of "British" and "exit".  "Smog", a combination of "smoke" and "fog", is another example of a portmanteau word.  The linguistic application of portmanteau (a hinged traveling case) was explained by no other than Humpty Dumpty to Alice in Lewis Carroll's Through the Looking-Glass:

"You see it's like a portmanteau—there are two meanings packed up into one word."

I think one of the cleverest uses of an initialization can be found in Episode 9 (Scylla & Charybdis) of James Joyce's Ulysses. One of the fictional characters of the novel, Stephen Dedalus, has borrowed money from the real-life Irish writer and painter George William Russell who had adopted AE as his nom de plume.  In the midst of a literary debate with Russell (AE), Dedalus suddenly recalls that Russell had lent him money (either a pound or a guinea).  He then thinks "A.E.I.O.U." as in "AE, I owe you".  Dedalus conceived this pun from the terminology of formal logic by adding "U" to the letters used to reference the four forms of categorical propositions in which "A" is the universal affirmative, "E" is the universal negative, "I" is the particular affirmative, and "O" is the particular negative.  Then, again, Dedalus may have simply been thinking of Frederick III, the Holy Roman Emperor, or just vowels.

Children_Dancing_on_the_Strand_by_AE_(George_William_Russell),_Ireland,_1914,_oil_on_canvas_-_Chazen_Museum_of_Art_-_DSC02714Children Dancing on the Strand by George William (AE) Russell (1914)