And please excuse the punctuation typo in my next to last response. Responding and editing on an iPhone has its positives and negatives!

In any case, this post was so interesting that I will have to squeeze some time at some point to do some more research, and see what pops up. It's anyone's guess what might evolve. Thanks for noticing!

@Jasper Actually, African-Americans have several dialects, just as regionally-derived as any other American. That has nothing to do with Ebonics, which is not a purely linguistic designation, but was created in a very dubious political context. I was very much a part of that conversation. In any case, the relevant point here is that you need to show some evidence that this is first even a mispronunciation vs. an alternate or comparatively outdated pronunciation, and secondly, that it is rooted in any African-American contribution to our language. It's cool to debate, however, but it shows a skewed set of priorities that the shtr- vs. str- difference is anything but noticeable (I'm talking about the "oh-how-annoying" comments.). But everyone is entitled to an opinion.

If you'll note: This alternate pronunciation is found among people of all levels of education and background. "Black" does not equal "Uneducated", by the way and "Ebonics" is not universally accepted among African-American scholars, although the concept of language evolving in conjunction with culture is. Keep race out of it, please. It is quite possible, as it is with many words and pronunciations that originate in Old English - a relative of German, by the way - that this may also be a holdover that has not fallen by the wayside. Like "offen" vs. "often" for the pronunciation of "o-f-t-e-n". Just my two-cents.