Not sure of the TV explanation but in the comics, Superboy finds Mon-El and he has no memory of his past so is thought to be a Krytonian until later on when the truth comes out. He choose the name Mon-El as he was found on a Monday & Clark real last name is El (this story was from the early 60s-kinda corny writing then).
So having that name makes no sense just like it makes no sense for the real Hank Henshaw to be called "Cyborg Superman." He was a villain for awhile and then took on Clark's appearance when Clark was "dead" and was one of 4 new Supermen who appeared on the scene & the world (& the readers) had to guess which one was the real one (turned out none of them were).
if man is 5
then the devil is 6
if the devil is 6
then God is 7
and if God is 7

Thanks. Well they aren't? They do kiss, it seems like a love kiss. That's all there is to Kara and Mon-El? The Comic, She says it's for luck. So there isn't anything after that?

That explains it in the context of the comics but you think they would have come up with something to explain It on the show. The House of El thing has been talked about quite a bit and now someone has the same last name and from an enemy world. They can't just put that out there and not address it or maybe they will.

In the comics Superboy thought Mon-El was from Krypton . Mon-El was in a ship built by Jor-El (I think there were some writings by Jor-El as well).Thats why Superboy thought Mon-El was family . Superboy gave him the name Mon-El because they first met on a Monday .

In the comics Superboy thought Mon-El was from Krypton . Mon-El was in a ship built by Jor-El (I think there were some writings by Jor-El as well).Thats why Superboy thought Mon-El was family . Superboy gave him the name Mon-El because they first met on a Monday .
This.
"I'm the ultimate badass,you do NOT wanna f-ck wit me!"Hudson,Aliens

In the comics Superboy thought Mon-El was from Krypton . Mon-El was in a ship built by Jor-El (I think there were some writings by Jor-El as well).Thats why Superboy thought Mon-El was family . Superboy gave him the name Mon-El because they first met on a Monday .

My guess is that Lar Gand is the prince and Mon-El is a fake name.
Also, this:
http://supergirlmaidofmight.com/images/Supergirl vol5 51-10.jpg
http://supergirlmaidofmight.com/images/Supergirl vol5 51-11.jpg

Mon-El's real name on Daxam is Lar Gand. The writing on this show is truly abysmal.

In the comics Mon-El and Supergirl were never a couple. He really was part of the Superboy comic series. Now that they have changed the DC universe and Superman was never Superboy Mon-el's name and origin has changed.

I wondered that as well, I remembered that hers was Zor-el. Mon-El is in the comics, those that read them. Tell me, about what happens with Supergirl and Mon-El? A couple? They said something about getting together. Are they talking about all of season 2 or just episode 3? Do they mean her being a mentor, training him, or a romance? Superman found him not supergirl? I watch the superhero shows, don't read the comics. They probably make changes, so that's a change?

That actually makes sense as it directly connects it to Superman as opposed to an alien randomly having the same last name.

Yeah, Superboy also thought he was his older brother as well, (Mon-El had amnesis) hence the El last name. They couldn't do that with Kara as she was old enough to know her family before she left Krypton.

That question will probably be left unanswered because in the comics, he's named Mon-El because Superman found him on a Monday and El is Superman's last name (Kal-El).
I guess the found the reasoning too silly to adapt.
Don't Jdg a Bok by Its Move

Well in the comic book canon the El last name was fairly common on Krypton, so I guess they are claiming because their planets are so close together they shared a lot of the same culture?
They pretty much had to keep the name as that is how he is most recognized by comic book fans.

I wondered that too!