S as a ranking above A originates from Japanese games.
Aside from Metal Gear Solid 4 , it has also been used in other games, such as Gran Turismo series (driving licenses), Devil May Cry (level performance), Final Fantasy VII (chocobo classes), Guilty Gear (character rankings), and countless others.
While the origin is universally acknowledged as Japanese, apparently, no one really knows what it actually stands for.
It's been speculated that it stands for anything from Super to Special , but there's no confirmation that I can find of any sort of "official" meaning.
Giant Bomb's S-rank article states that because C was the lowest passing grade in the Japanese school system, "S" was used to allow for a wider range of grades.
See the following excerpt: Originally created in Japan where anything below grade ‘C’ was considered a failure.
The 'S-Rank' allowed for a wider range of obtainable grades and thus player motivation, meaning that it was soon adopted by western developers who realized that the ‘S-Rank’ was much cooler than the boring ‘A’.
An A rank is commonly obtained by getting a 90% to 95%.
If the player is flawless or achieves perfection in something, it qualifies as an S .
Many people have wondered what the S stands for… Special?
Super?
No one knows for sure.
The Rank Inflation article on TVTropes mentions the S-ranking as well, however, without any speculation on the origin:
But then what about the players who are really looking for a challenge for whom mere golds aren't enough?
The solution — give them platinum medals to aim for.
A-grade not good enough for you?
Go for A+, or S. Sometimes, even these inflated ranks are subject to inflation, with A being about average and the real goal being a more different S rank: SS or even SSS.
Urban Dictionary's S-Rank article (linked article is SFW, but the site itself can have some very NSFW content) also lacks a concrete origin: Something that is so superlative that it cannot be described by any traditional ranking system.
It is A++, 11/10, six stars, and three thumbs up.
In rare cases, something can be so exemplary that it becomes SS or even SSS-rank.
Many people have wondered what the S stands for.
Special?
Super?
Schwarzenegger?
No one knows for sure.
Comes from Japanese video games, like the Devil May Cry series, where A-rank just wasn't good enough.
In addition, all 3 of these sites are editable by anyone on in the Internet, so I'm not sure that any of these can be considered concretely reliable, and the assertion on the Giant Bomb article that it's related to the Japanese grading system has no source and isn't one I can confirm because I am not familiar with the system.
Basically, as the TVTropes article stated, it's just a way for there to be a ranking that is better than the "best", similar to how some games have Platinum medals on top of Gold.
gaming.stackexchange.com/users/160/FAE
S stands for "shuu" (秀), which is Japanese for "excellent".
I comes from the usual Japanese grading.
Just like how we have A+, A, B, etc.
They have their own system which is the same as ours except that instead of A+ they write "S".
I am attending university in Japan and had to have this explained to me because I didn't know what the "S" grade on my grade report was.
gaming.stackexchange.com/users/79304/Kimberley
There's not a lot of sourced information about the origins of this term, although there's a fair number of plausible explanations : Originally created in Japan where anything below grade ‘C’ was considered a failure.
The 'S-Rank' allowed for a wider range of obtainable grades and thus player motivation.
The TV Tropes term for this is " Rank Inflation :"
But then what about the players who are really looking for a challenge for whom mere golds aren't enough?
The solution — give them platinum medals to aim for.
A-grade not good enough for you?
Go for A+, or S. Sometimes, even these inflated ranks are subject to inflation, with A being about average and the real goal being a more different S rank: SS or even SSS.
Having a rank above "A" also means that it can be somewhat more secret, some extra or additional goal to shoot for.
Prior to the widespread adoption of achievements, offering a "S rank" was a way to reward your most devoted players.
gaming.stackexchange.com/users/13845/agent86
I was going to come to the rescue with Gran Turismo, whose S License is higher than B or A (or their variants), and which actually says what S stands for right in the game!
And then I looked around for an actual screenshot (well, videos), and discovered that it's not consistent even within this series: Gran Turismo 2: " Special " Gran Turismo 3:
" Super " Oh well.
gaming.stackexchange.com/users/31663/Ken
According to the Japanese Wikipedia article 特別 (Special) または優れた (Superior) の意味で、A級のさらに上位の階級を表す。S級、S席など。
My translation: With the meaning of Special or Superior, it is used to indicate a position above Rank A. Rank S, Position S, etc.
gaming.stackexchange.com/users/49311/ortiz
Special, Secret, or Super are the most common meanings.
There's no real reason for it, other than to say something akin to "This is better than good!"
gaming.stackexchange.com/users/7794/Hyppy
In some (generally Japanese) games, the best rank is S.  For example,  this question  talks about getting an S rank on story battles.   Metal Gear Solid 4  ranks their weapons on an SABCDE scale.   Does S mean something special?  Why is it used?
In some games, the rank above A is S. What does S represent?
gaming.stackexchange.com
<terminology>
gaming.stackexchange.com/questions/70673
gaming.stackexchange.com/users/5398/Steve V.
The origin is Japanese but no one knows what it stands for. C was the lowest passing grade in the Japanese school system. S-rank allowed for a wider range of grades. The letter S in ranking, seems to be used commonly by eastern developers and represents a grade such as Special.
The community suggests that the origin of S rank comes from East.