a) When you say that you knew about, do you mean that you have heard tell about other things?1900
a) Maria and me concluded that we had struck one o' them gamblin' places we'd heard tell about, and I tell ye we got out in a hurry!1901
b) I never heard tell of it until I was told by Justice Bolte about it.
a) "I niver heard tell that you had an owl in your parlor chimney," said he, sort o' suspicious-like.1904
b) And we had a gentleman in our county that perhaps most of you have heard tell of,
a) I asked him if he had ever heard tell of a bouse they called the House of Shaws.
b) "Never heard tell of him," said John William, making spectacles of his burnished bores, and looking through them into the sunlight.
Originally, I selfishly assumed "heard tell" was an American English slang construction, but upon a little Google Ngram sleuthing, I discovered it is a common English construction.
Though details differ, the general pattern is clear: A general rise in frequency throughout the late 1800s, peaking at the turn of the century, a general decline throughout the 20th century, then a leveling off around the mid 1970s. The American English usage was a lot more unpredictable, a bit choppy, but generally follows the same pattern.
But what interests me most is the red line in all of the above graphs. That's the one that plots the frequency of the tri-gram "heard tell of". This stung me a bit because my brilliant native speaker intuition strongly preferred "heard tell about", but in this I am in the minority.
For the graph impaired: What the red line in the above graph tell us is that when English speakers have used "heard tell", they most frequently follow it with "of" even though they have a semantically similar choice available, namely "about" (and even "that").
I don't have a semantic analysis of the difference between prepositions (though I don't doubt an interesting one could be engineered), but after I consoled my wounded linguistic pride, I then realized that the construction with the preposition "of" strongly tracks the overall pattern. The bigram search "heard tell" is a more general and inclusive one, hence its results include all of "heard tell of" results as well. If you imagine taking away everything underneath the red line, there would not be much left, less than half to be sure. This means that "heard tell of" accounts for more than half of all instances of "heard tell".
I don't know why "of" became so tightly associated with the "heard tell" construction, but it struck me as a nice example of how construction semantics are not necessarily compositional, intuitive, or even necessarily coherent. I wonder if these three choices "heard tell of/about/that" have regional variances? We will need a more nuanced corpous to tease that out.