"vixen171211hannahhaystheycanneverknow" could be a username or a unique identifier chosen by a user, possibly for a social media platform, gaming community, or another type of online service. The inclusion of what appears to be a date ("171211") and names ("hannah") suggests it could have personal significance.
The string seems to break down into several parts: vixen171211hannahhaystheycanneverknow high 2021
in a "forbidden" or "secret" relationship dynamic, which is reflected in the title " They Can Never Know ℹ️ Important Context possibly for a social media platform