In general, Esc aborts an action (uploads, page loads, anything in progress) or is used to regain control over the interface (fullscreen, video playback). Those are the contexts in which users will have used it, if ever at all even for these.
The way to implement it is as an augmentation to allow keyboard focused users additional control. You can implement it with the off-chance that for some users it will be a surprising, positive, user interface interaction. While for the rest of users, it will not matter if this interaction feature remains undiscovered.
However, keep in mind to use it with aforementioned common uses. Based on those observations, using Esc to go back in browsing history seems unintuitive to me, as the user is neither aborting nor regaining control. In fact, the backspace button might seem a better fit and in line with browser implementations for going back in history.
The best way to assert if users "get it" or use it is to implement a simple tracking of the click event. If you feel the benefit for power users justifies pushing the feature, you can also nudge users towards using it, for example by cues like a little text next to an icon that they would interact with my mouse, for example:
[x] (or press Esc)
However, be aware that implementing domain-specific behaviour is rarely a good idea, as it adds additional cognitive overhead and has to be learned in the first place.
Xat the top.Escto stop page loading, stop running scripts, cancel a pending meta-refresh, exit full-screen mode, etc. I most certainly do not expect it to go back, and I would think your site was horribly broken if this happened.esckey on websites in general, whereas in the question body you are concerned with using theesckey on a website as an equivalent to goingbackin browsing history - two very different concerns in my opinion.