Thank you @Abrita Chakravarty. I have done suggested modifications.
I have found 7 properties beginning with small letter "w", by Common Names:
In[1]:= Select[CommonName /@ EntityProperties["Country"], StringMatchQ[#, "w" ~~ __] &]
Out[1]= {"wage and salaried workers",
"wage and salaried workers fraction",
"wage cost index",
"water area",
"water productivity",
"waterway length",
"wholesale price index"}
and 9, by Canonical Names:
In[2]:= Select[CanonicalName /@ EntityProperties["Country"], StringMatchQ[#, "W" ~~ __] &]
Out[2]= {"WageAndSalariedWorkers",
"WageAndSalariedWorkersFraction",
"WagesCostIndex",
"WaterArea",
"WaterArrivals",
"WaterProductivity",
"WaterwayLength",
"Workforce",
"WPI"}
2 Canonical Names have Common Names that do not start with letter "w".
It looks so that the correct result is 7, as the formulation ask for names starting with the small letter "w"..