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 special language, 'ham speak', filled with many specific acronyms that takes time and effort to learn. {Hint: 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}