I was thinking (while making tacos, for those keeping score at home) that some monsters just have stupid names.
The Roper (okay - and I'm not kidding - when I hear the name the Roper, I think of Mr. Roper from Three's Company - if don't remember the show, ask your parents) - really? Shambling Mound. oooo - slow moving veggies coming for me... Whatever.
I get why ADVENTURERS would call them those things - but wouldn't people - normal people who are afraid of monsters - call them things like Tentacled Horror or the Bog Beast or something?
Does it matter? Nope, not at all.
When the PCs come to a village near a swamp being terrorized by the Nightclaw - and the only description is "large, dark, hides in the shadows - leaves claw marks on the walls and blood trails to the swamp" they have to decide what they are facing. Maybe trolls are common enough in these swamps that people see them all the time, but they usually attack in the daytime, and this is a nocturnal troll and since it doesn't act like people think it should, they think it's something different. Of course it could be a vampire or some other undead creature, it could be a small black dragon, a demon, etc.
Gasp! How do the PCs prepare to defeat this foul monster? Well, they do the best they can, they go find it, get their butts handed to them, run away (now they know it's actually a Wyvern that has moved into the area, not normally native to swampy areas, the locals have NO experience with the creature) re-equip and tackle the beast. Do they succeed right off the bat? No. But for me (even as a player) that's half the fun. Not knowing EXACTLY what is coming.
That's just a random thought off the top of my head.
Of course, stupid names can work in reverse, too. I had a PC try to hide away from his enemies. One night he heard a sniffing sound outside his cabin door. When he inquired to the locals what it could have been they told him the children's stories of the Snufflers - fat, hairy creatures that could sniff out a person even to the underworld. The player laughed at the name (okay with me, though I really thought he'd take the stories more seriously...) and dismissed it all as just children's stories until the bad guys kicked in his door...