I believe this pattern was originally popularized by "i18n" for "internationalization", partly for convenience and partly to have an identifier that would fit in legacy systems.
According to Tex Texin, the first numeronym of this kind was "S12n", the electronic mail account name given to Digital Equipment Corporation (DEC) employee Jan Scherpenhuizen by a system administrator because his surname was too long to be an account name.
('K9' is homophone for 'canine'. To be homonyms, two terms should have different meaning - if two terms share the same name and meaning, they are the same...)
