What humans will do to save themselves from typing a few characters: LOL. ROTFL. TTYL. <3. BRB. Universal sentiments and actions become encoded.
Well, imagine that each character had to be tapped down the line in Morse code. Telegraph operators had even more incentive to cut down on letters than did even the T9 texters of yore.
And so they came up with codes to communicate the things that they needed to say often. These were first codified by Walter P. Phillips into what became known as the Phillips Code in 1879. (It was updated several times, the last I found in 1975.)
Nearly all of these codes are now obsolete. But there is a small group of hobbyists who keep a few them alive. Amateur radio enthusiasts still use at least a couple of these abbreviations to this day as detailed by Glen Zook, call sign K9STH, in a widely reproduced brief history that relies on a 1934 Navy bulletin on the origins of '73.'
WIRE- Preference over everything except 95
1- Wait a moment
2- Important business
3- What time is it?
4- Where shall I go ahead?
5- Have you businessfor me?
6- I am ready
7- Are you ready?
8- Close your key; ckt is busy
9- Close your key for priority business (wire chief, dspr, etc.)
10- Keep this ckt closed
12- Do you understand?
13- I understand
14- What is the weather?
15- For you and and other to copy
17- Lightning here
18- What is the trouble?
19- Form 19 train order
21- Stop for meal
22- Wire test
23- All copy
24- Repeat this back
25- Busy on anr wire
26- Put on gnd wire
27- Priority, very important
28- Do you get my writing?
29- Private, deliver in sealed envelope.
30- No more -end
31- Form 31 train order
32- I understand that I am to .........
33- Car report (Also, answer is paid for)
34- Msg for all officers
35- You may use my signal to ans this
37- Diversion (Also, inform all interested)
39- Important, with priority on thru wire. (Also, sleep-car report)
44- Answer promptly by wire
73- Best regards
88- Love and kisses
91- Supt's signal
92- Deliver promptly
93- Vice pres. & gen. mgr's signals
95- President's signal
134- Who is at the key?
The list—a decidedly non-sexy counterpart to the telegraph's sexytime abbreviations—is mostly dedicated to basic traffic direction: stopping, going, clearing wires, assigning importance, etc. But 73 and 88 are different. They are ways of compressing sentiment, and helpful, I'm sure, in sending messages quickly across the wire.
Put another way: 88 was the fastest possible way to transmit love. It was the emoji heart of its day. (It's something else today, sadly.)
Humans now have zillions of ways of abbreviating our emotions for easier transmission along the network.
And way up the evolutionary tree, at the beginning of the electrical era, we find this common ancestor, 88.