Murder Hobo, Munchkin, etc.. sort of derives from early Role-playing gamer experience where players thought the whole point of the game was to simply go kill stuff.
EG: start level 1 character party.. go to goblin caves, kill goblins, go to kobold caves, kill kobolds, go to bandit cove, kill bandits, etc, etc, etc.
The Role-playing systems often exacerbate this concept of "killing = good", because many systems reward XP or skill points or whatever rewards for advancement after things are killed. (EG: In D&D, monsters have XP values for being defeated. The problem is that younger players think "death = defeat", while more mature players see "defeat" as a more abstract concept.. like if you have a band of thieves find a way to sneak around the goblin patrol, then it could technically count as "defeating" the patrol.. or if they find a way to diplomatically resolve a conflict, then the enemy is "defeated" in that they are no longer a threat).
Another aspect that rewards "kill everything" game play is the looting. Parties go kill stuff, they get to loot the battle field and find all kinds of good stuff.
So, this compounds into this "kill everything, loot everything, level up" mentality.
And, it's ok when dealing with very simple adventures like "go kill the goblins" or "go kill the bandits".
But, it clashes when the game master tries to have more complex adventures.. like the characters need to go into town and speak to NPC's to investigate a murder or kidniapping, or ... basically do a lot of non-combat stuff.
The players eventually have to mature and move on from "kill everything, loot everything, level up" mind-set to "I'm playing because this is fun and I want to help everyone have a fun time".
Some don't. They stay stuck in "kill, loot, level" mode..
So, you end up with stereotypical situations like...
"We're gonna go to the local weapons shop. Oh, the shop owner has really cool stuff, but we can't afford it. Ok, we attack the shop owner, kill them, take all their stuff. How much xp and loot do we get?"
And the GM is sitting there going "ok, now the guards are coming after you, because you did this in a heavily populated place.. and you just committed murder and theft!"
After the first time of this happening, some players wise up. But, there will still be that one player (or even that one crazy party of players) that go...
"Ok, we kill all the guards, too."
They they head on to the next town and just do the same thing over and over and over.
"Hobo" in English language refers to a homeless wanderer, often traveling from town to town via the train / rails. Hobo had a derogatory / negative meaning, because it was often associated to poor people that coulnd't make it in the real world... either having mental illness or not willing to work or whatever.. basically shunned by society. Hobo's would sleep wherever they could (under bridges, in rail cars, in abandoned houses / warehouses .. and they'd scrounge for whatever they could to survive.
So, a band of murdering adventurers going from town to town would be slandered by being called "murder hobo's"
It's sort of common to have ONE player act like a murder hobo... it's often the one player that makes the combat character, and wants to solve all problems by killing them. The rest of the party tries to keep them in line, but sometimes that jerk player gets everyone into trouble.
But, if an entire party is murder-hobo'ing.. then that's just really bad, and is often the result of a GM / DM conditioning them to be that way by rewarding that kind of behaviour.
What's really bad is when the players disregard their character's alignments to be murder hobo's.
EG: if the party was filled with lawful good clerics and paladins, but went around slaughtering normal, decent people in towns just to try to get XP and loot... it would totally go against the character alignment.
So, basically, Murder Hobo'ing is an insult to gamers that haven't matured, and think Role-Playing is just about kill, loot, level.