This is to avoid trademark dilution, which in the USA can invalidate a trademark. Aspirin, for instance, used to be a trademark of Bayer, but these days is generic.

I did not regularly hear the term "game console" until the late 90s. I used to think the promotion of this term was done by Nintendo in a trademark-protective maneuver to avoid rival systems being called "Nintendos" by granny, but it seems I was mistaken. Nevertheless, in the 80s we called them systems. Which system do you have, Nintendo or Sega?

Recently in my retrogaming media habit I've heard "console" used occasionally to describe video game consoles in advertisements dating back to the early 80s, but at that time it was also used by Texas Instruments to refer to the TI-99/4A computer. TI was naming all of their home products to give a space-age technical feel to them. They marketed joysticks as "Wired Remote Controllers", and cartridges for the TI-99/4A as "Command Modules" or "Solid State Software". So I don't think "console" referring to a gaming device specifically was a term of art back then.

Aspirin is kind of a special case - while it had become generic in the usual way, the actual loss of trademark status was part of the Treaty of Versailles as a punishment for world war 1. (So while there are various trademark-protection strategies, "don't lose a world war" might be difficult to pull off :-)

Oh man, time to fire up my TI-99/4A again.