Regarding this article on Autopia via Wired.com: How Carmakers Play The Name Game | Autopia | Wired.com
Go read the article, I’ll wait, or here is the key part we’ll be talking about:

Automakers such as Acura and Cadillac have followed the lead of Mercedes and Lexus, abandoning “Coupe d’Elegance” and “Integra” for CTS and TL. Sutton says such tactics convey an “insider” status for owners and help promote a brand over a particular model. Abbreviations and numbers are “like a secret language that you learn as an enthusiast and owner of the luxury car,” but “it also requires that the parent brand carries all the weight and communicates all of the brand message.”

The first Cadillacs were made in 1902, and simply referred to as Cadillacs.  Beginning in 1903 all one cylinder cars were referred to as Cadillac Model A, which was the way that many early car manufacturers designated their first model in the early 1900’s.  Later Cadillac used letter, then number designations, then names for their models.  Now they have turned to letter sequences; I think it is incorrect to say that this is something ‘new’ for Cadillac.

1941 Cadillac Sixty Special copyright GM

Here is a (I am sure partial) index of names Cadillac has used over time; I have omitted re-used names.  Please feel free to comment and correct any omissions and I will edit / update:

1902 Cadillac
1903 Model A
1904 Model B
1905 Model C, Model D, Model E, Model F
1906 Model K, Model L, Model M
1907 Model G
1908 Model S, Model T
1909 Model 301917 Model 55 (V-8)
1920 Type 59
1926 Series 314 (now named after the cubic inches in the engine), Custom Line
1930 Series 353, Fleetwood Line, “Flat Windshield” models, Madame X Models
1936 Series 60, Series 70, Series 75, Series 80, Series 85, Series 90
1937 Series 61, Series 65, Series 60 Special
1941 Series 63, Series 67
1946 Series 60 Special Fleetwood
1953 Series 60S, Series 62 Eldorado Special
1959 Fleetwood 60 Special, Series 63 DeVille, Series 6200 (or Series 62)
1967 Calais, DeVille, Fleetwood Eldorado, Sixty-Special, Fleetwood Brougham
1974 Fleetwood 75, Talisman Brougham
1984 Seville
1987 Brougham, Allante, Cimarron
1997 Catera
1990 STS (Seville Touring Sedan)
1993 ETC (Eldorado Touring Coupe), ESC (Eldorado Sport Coupe), SLS (Seville Luxury Sedan)
1999 Escalade
2001 DHS (Deville High Luxury Sedan), DTS (Deville Touring Sedan)
2003 CTS (C-class Touring Sedan)  [also at this point STS was re-purposed in some media as S-class Touring Sedan]
2004 XLR  (Experimental Luxury Roadster), SRX (S-class Recreation X-over (Crossover)), V-Series (Velocity)

I have omitted some combinations, like the Eldorado Seville, or Eldorado Biarritz.  Where I have shown names to explain the letters, those were historical.  In some cases Cadillac now says that names such as CTS or STS are simply the name and not acronyms.

So, letter and numbers are nothing new for Cadillac, but are actually ‘old school’.  I would like to see Cadillac re-use some of the historical numbers, such as 60S again, or Series 75 for the planned replacement for the DTS/STS, but I think it will be named XTS (Experimental Touring Sedan).  Also the ‘smaller than a CTS’ model that is on the way will likely be named ATS, which would be A-Class Touring Sedan if it were an acronym.

Article Reference: Autopia via Wired.com: How Carmakers Play The Name Game | Autopia | Wired.com.