Well this isn't the complete answer but I quote from a recent edition of
Amateur Photographer:-

"This year Nikon celebrates the 75th anniversary of the launch of its
first lens in March 1933, a lens for aerial photography. The brand name
was formed by adding a "r" to an abbreviation of the firm's name "Nippon
Kogaku". It followed the European practice of lens names ending in "r".

So it looks like there was an element of copy-cat involved.

No idea, but there's plenty of them - Pantar, Lanthar, Planar, Skopar,
Protar, Artar, Biotar, Biometar, Heliar, Summar, Summitar, Elmar, Xenar,
Xenotar, Solinar, Ektar, Omegar, Symmar, Ronar, Sironar, Serenar,
Thambar, Takumar, Glyptar.

I can't think of  many '-or' names - Nikkor, Dagor, Rokkor, Hektor.

Of course there's also Flektogon, Ultron, Neonon, Rodagon, Epsilon,
Hypergon, Grandagon, Summicron, Biogon, Distagon, Angulon, Pentacon,
Orestegon, Omicron, Variogon, Claron, Meogon, Componon, Imagon,
Rokinon, Nokton, Holgon, Xenon, Pokemon ...

Just testing.  :-)