73 and 88 have special meanings in 'ham speak' - the special language used by radio amateurs! Here is an article on the history of these terms...
Oh, hams have their own special language, 'ham speak', filled with many specific acronyms, technical terms and special meanings. It takes time and effort to learn the language, but most hams enjoy explaining all the details, just ask one. {Hint: You ca use "wikipedia.com" and the "ARRL.org" sites to search for meanings of unknown acronyms! - you will catch on quickly.}
Phonetics and "Q-Codes" are other types 'ham speak'. Check out our page "Phonetic and Q-Codes" page. Hams picked up and still use the Western Union "92 code" {see below}