As an element of backwards rationalisation, my brain interprets "ENOTTY" as "E-NO-TTY" (Error: NO TeleTYpe available) which is the rough current meaning, rather than "E-NOT-TY" (Error: NOT a TYpewriter) which is the original meaning.
I’m pretty sure it is ENO-TTY. Because who among us hasn’t started up our computers only to realize that our terminal had been replaced by the renown ambient electronic artist?
Your interpretation seemed so obvious and natural to me that I never once considered it could have a different etymology, until now.