Title is self-explanatory. It’s obviously an engrish/translation thing, but what does the original Japanese title mean? What would be a non-nonsensical translation for it?

The Japanese name of the game is Koutetsu no Girlfriend, which does indeed translate to "Girlfriend of Steel". Oddly enough, the game actually has an English title as well, Iron Maiden, even though the game wasn't officially released in English. I assume that "Iron Maiden" is referring to the torture device and not the heavy metal band, but who knows?

Of course, that raises another question... If the game's English title is Iron Maiden, why does everyone in the English-speaking fandom call it Girlfriend of Steel? I haven't a clue. Maybe people just didn't want to get mixed up with the heavy metal band, ha ha! As for WHY the game is called Girlfriend of Steel or Iron Maiden, maybe it's referring to the fact that Mana pilots a giant robot? Although I guess that wouldn't explain why the spiritual sequel, which is a separate continuity and does NOT have Mana in it, is called Koutetsu no Girlfriend 2nd ("Girlfriend of Steel 2nd")... and yes, it also has an English title, Iron Maiden 2nd. For example, you can see the Iron Maiden 2nd title on the cover of the guidebook to the Playstation 2 version, which I reviewed here: Shin Seiki Evangelion Koutetsu no Girlfriend 2nd Koushiki Visual Book

I hope that helps a little, even if it doesn't completely solve the mystery.

Given that the NWOBHM band is named for the torture device...

I suspect there may be some dancing around intellectual property laws going on -- ISTR something a couple of years back where a band sued for the misuse of its name, and the Iron Maiden thing came to mind at the time. It's not quite so direct as the example of JJBA, where the original names are obvious and direct allusions to pop and rock bands or tracks (Santviento -- pronounced Santana, for example).

Asking the important questions here.

I came across some obscure information - which I can't provide right now, but I'll ask the people who found out - that Mana is essentially a conjunction of old plans King Records had to insert into the show that were reused for GoS 1. I assume the actual name is probably just usual 90s cool factor Engrish, but there's probably some sort of "definitive waifu for you, customer" factor involved.

FelipeFritschF wrote:Asking the important questions here.

I came across some obscure information - which I can't provide right now, but I'll ask the people who found out - that Mana is essentially a conjunction of old plans King Records had to insert into the show that were reused for GoS 1. I assume the actual name is probably just usual 90s cool factor Engrish, but there's probably some sort of "definitive waifu for you, customer" factor involved.

What do you mean by this? That Mana was actually supposed to be a character in the anime at some point?

Also lol, I guess knowing that “girlfriend of steel” is actually an unlocalized Japanese title makes sense. Maybe fans use it because it sounds so ridiculous over the kinda vanilla “Iron Maiden”.

I always thought it obvious that it's a referece to how Mana is one of the Trindent land cruiser pilots?

It's obviously a play on words of the phrase "heart of steel". Here's the meaning of it:
If someone is described as having a "heart of steel," it means that he or she is not swayed by any emotion. This is an English idiom used to describe people who prefer to let their judgment be based on facts or other data rather than anything that might sway their hearts. The phrase also implies that the person who is described in this manner can be cold and tactless in his or her dealings with other people. "Heart of steel" is one of many idioms that use the heart's symbolic place as the location of all human feelings as the basis for its meaning.
Individuals with a "heart of steel" are unlikely to ever get too emotional.

Unfortunately, that holds absolutely no water when you look at any of Mana's interactions. If we were talking about Rei here, sure why not, but Mana is far from being unswayed by emotions

Literary Eagle wrote:If the game's English title is Iron Maiden, why does everyone in the English-speaking fandom call it Girlfriend of Steel? I haven't a clue.

To be honest, this also intrigues me. It's so weird. Anyway, I kinda got used to saying Girlfriend of Steel when I speak in English and Iron Maiden when I speak in Portuguese and Spanish hahaha.

Literary Eagle wrote:s for WHY the game is called Girlfriend of Steel or Iron Maiden, maybe it's referring to the fact that Mana pilots a giant robot? Although I guess that wouldn't explain why the spiritual sequel, which is a separate continuity and does NOT have Mana in it, is called Koutetsu no Girlfriend 2nd ("Girlfriend of Steel 2nd")

I also thought about that. "Well, maybe it's because Mana pilots T•RIDEN•T. So, why did the second game keep the name?" If that's truly the case, it's probably because of brand recognition. Honestly, Girlfriend of Steel 2 could have had any other name. It's just another generic visual novel and has nothing to do with the original game. My bet is that the team behind it came up with the "spiritual successor" shenanigans to get the consumer's attention. Not that the first game is great, but it is mildly popular.

Pantsu Lover wrote:It's obviously a play on words of the phrase "heart of steel".

That's cool. However, if you think about it, neither Asuka nor Mana are like that.

Blockio wrote: Mana is far from being unswayed by emotions

Mana has to hide her emotions to fulfill her mission.
As i remember, she's sad deep within inside, but have to pretend she's having fun while her teammates are getting killed over and over.

That seems to be overthinking it a bit there's not even thatmuch emphasis.

She's associated with "Steel" cause she pilots an actually mechanical mecha. Or cause her ex shows up in one, anyways.