While I can't answer that question from a historic point of view (which might get this answer deleted, I'm aware of that), I'd like to say a few things about the biochemical/neuroscientific basis of mint flavor.

TL;DR: We are not "conditioned" to perceive mint flavor as fresh. The responsible molecules in mint actually do evoke a "fresh" sensation.

You see, usually "flavor" consists of two different neurochemical components. The first is the activation of taste receptors on your tongue - they are responsible for the five basic tastes: Sweet, salty, sour, bitter, and umami (savory/meat-like). But if you ever had food when having a cold, you know that this isn't all. The more complex flavor patterns are the result of the activation of olfactory (smell) receptors in your nose.

But there's a third class of receptors, which actually aren't considered taste or olfactory receptors. These are called the TRP channels, they are a rather large protein family, and they have several functions in the body. Two of these channels are interesting when it comes to taste, and these two are temperature-sensing.

The first is called TRPV1, and one of its functions is to detect heat. When your food's too hot, they activate and tell you it's too hot (in terms of temperature) by sending a pain signal. But the protein does not only get activated by heat, but also by capsaicin, the active ingredient in pepper, chillis, and tear gas. That's why "hot" (in terms of taste) is exactly that - a "hot" (temperature) sensation (Edit: not in pepper, that's piperine, which also activates TRPV1. Thanks to /u/BloomsdayDevice).

The other one is called TRPM8, and it's the equivalent "cold receptor", reacting to low temperatures. Now guess what also activates this receptor? Menthol, the active ingredient in mint. So it's not that at some point a company decided "let's make mint the "fresh" flavor", and everybody just went with it, but rather that there weren't really common alternatives to mint that activated the (at that point unknown) TRPV8 TRPM8 ion channel.

Edit: Spelling.

Edit 2: Mixed up TRPV and TRPM in the last paragraph. Also, is thanking for gold encouraged or discouraged here? Anyway, thanks ;)

Edit 3: Was wrong with pepper.

Hello everyone,

Unfortunately, we have already had to remove a number of poor quality responses in this thread, including many asking about the deleted comments, which merely compound the issue. In this thread, there have been a large number of incorrect, speculative, or otherwise disallowed comments, and as such, they were removed by the mod-team. Please, before you attempt answer the question, keep in mind our rules concerning in-depth and comprehensive responses. Answers that do not meet the standards we ask for will be removed. Finally, the only answer that was in any depth did mention the science behind mint, but did not address the historical question OP was asking.

Additionally, it is unfair to the OP to further derail this thread with off topic conversation, so if anyone has further questions or concerns, I would ask that they be directed to modmail, or a META thread. Thank you!