It is my understanding that the acronym "TARDIS" was coined very early on in Doctor Who by the Doctor's granddaughter, Susan, giving a name to the wondrous vessel they travel in.
These vehicles were common amongst Time Lords, so my question is why was the name coined only then rather than there being a pre-existing name for these vehicles?
Furthermore, how does the name catch on with other Time Lords and other species aware of these vehicles? For a human comparison, wouldn't it be similar to giving your own car a nickname while everyone else would still refer to it as a "car"? If your granddaughter called your car "TARDIS" other people would still refer to it as a "car", it's original universally recognised name, rather than whatever you or your family call it.