This question already has an answer here:
I have recently asked Is there a short term to describe long technical terms abbreviations? which is related to software development terms such as i18n.
I have quickly got an answer that pointed to the exact answer:
Alternatively, the letters between the first and last are replaced with a number representing the number of letters omitted, such as "i18n" for "internationalization". Sometimes the last letter is also counted and omitted. These word shortenings are sometimes called alphanumeric acronyms, alphanumeric abbreviations, or numerical contractions.
I have initially thought of asking this on English, but these term seem to technical that software engineering seems more appropriate.
I can understand if this was considered offtopic for some other reason, but it is clearly not opinion based.
Related meta question: Why is this terminology question considered as “opinion based”?