English spelling does not represent original spellings in other languages, except when it does. Certainly there is no consistency or reason why some words are spelled some ways and other words are not. Asking "Why?" some English words are spelled (or not spelled) some particular way alway has the same answer: That's the way it is.

There are plenty of other words from Latin that start with j, like judge, jury, jar, join, etc. Probably none of those words came directly from Latin, though. They mostly came from French, where they were already spelled with a j. Why were they spelled with a j in French? That is an interesting question....but unfortunately not a question about English.

Fortunately, this has been discussed on the site where it's a better fit: linguistics.stackexchange.com/questions/43933/…

There are just jillions of them: January, June, July, joke, jest, jactation, jacent, jacinth, jamb, jealousy, jejune, jelly, jettison, jetty, jetsam, jocund, joint, jostle, journal, journey, jovial, joy, jubilation, judiciary, juice, Julian, junior, juniper. Honestly, given how a gust of wind doesn't sound anything like being just of mind, so why in the world would we ever want to spell those two the same?

You're forgetting the biggest of them all-- "Jesus." In Latin, "Jesus" is spelled "Iesus," also the word "Jew" being derived from Latin's "Ivdæus," hence the inscription "INRI" above Jesus on the cross, standing for "Iesus Nazarenus Rex Ivdæorum," or "Jesus of Nazareth King of the Jews." The same goes for Julius Caesar, whose name in Latin is "IVLIVS CÆSAR," the month of July being named after him, which in Latin is "Ivlii." BTW, Caesar came to Rome from Greece at 14, so Latin "Ivlius" is his birth name "Ιουλος" (Ioulos) Latinized.

I cannot see how this is opinion based.

The opinion is yours, that English spelling should be regular in the way you expect it to be.

That's just the way it is.

This is a juvenile dispute.

This is a great question, especially for ELU. I'm not sure why people are being so petty about closing it. If you don't know anything about the varieties of 'j' and 'g' then at least let someone who does have an idea give it a try.

Surely it's because English changed the initial 'i' into a consonant in all these words, so we needed a different symbol to represent the sound. It's the same with 'u' and 'v', which were the same letter in Latin. (The Romans used V in carved inscriptions because straight lines are easier to carve.)

Good question and I believe it is answered here: If the letter J is only 400–500 years old, was there a J sound that preceded the design of the letter?

This question is not particularly focused, but I concur that the duplicate probably answers what is being asked.

To the other part of the question, –age is French, from Latin –aticum.

The original question is trivial and shows no research: all 3 words are from old French and give or take a vowel are spelt the same; any dictionary with the most basic etymology information will tell you that. But if there's a more interesting question, the OP is free to ask it.

Because if we mis-re-spelled just as gust, then we'd have to pronounce it the wrong way too. This is actually a question about French, not English.

The word language is written with two gs. The second is modified by e to become /dʒ/. Note that the first is followed by u and retains its hard-g sound /g/, just as gust does and gustice would if that were a word. Perhaps that's the answer you're looking for.

I'll reöpen this once because you seem so determined. But understand that language was never a word in Latin. Once Latin eventually adopted its G, that letter could only ever have the value it has in English God, no matter whether the word was Gaius or grave or regimen or gemma or genus or legion. Those all shared the same unchanging [g] sound in Latin.

lingua and iustitia in their Latin forms and English forms (language and justice) have zero in common in either one. There are two different sounds.