Stdev (MSExcel function name) measures dispersion in a sample. In the context of historical vol, stdev indicates
2) how Fast price swings
If you plot log(periodic Price Relative) in a histogram, it will be a bell curve. Periodic typically means “daily”, meaning we compute closingPrice(Day N)/closingPrice(Day N-1) and plot the log of these price relatives in a histogram.
Any such bell curve will Flatten (scatter) out if the sampling period lengthens from 24 hours to 7 days or 30 days, but a high historical-vol means a flat bell curve at a high sampling frequency (such as daily or hourly).