apropos of absolutely nothing, trigrams that occur only twice in the CMU pronouncing dictionary word list, along with the words that contain them (where edit distance between words is greater than 3) https://gist.github.com/aparrish/099b4d7ecd36b2e7e02ad0d0905a8b67
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(mostly turns out to be place names or personal names, but there are some nice ones in there like "subpar, webpage")
