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Thank you - that provides more finer exploration of the matter! It also reminded me about existence of the words file on *nix machines, just in case someone wants to use it one day.

In[1]:= words = Import["/usr/share/dict/words"] // Flatten;
wordsLength = Length[words]

Out[1]= 235886

It has some lengthy words, which I won't try pronouncing:

In[2]:= Select[words, StringLength[#] > 23 &]

Out[2]= {"formaldehydesulphoxylate", "pathologicopsychological", \
"scientificophilosophical", "tetraiodophenolphthalein", \
"thyroparathyroidectomize"}

BarChart[((StringCases[words, ___ ~~ # ~~ ___] // Flatten // Length)/
      wordsLength*100.) & /@ Alphabet[],
 ChartLabels -> ToUpperCase@Alphabet[], PlotTheme -> "Detailed"]