Is there any etymological connection between "whisper" and "lisp"?
Both involve speech, have an "isp" sound, and a lisp can sometimes be quiet like a whisper...
Although, I haven't found much connecting them directly, except a report that in German:
lispeln = to lisp, to whisper
And that was from the The Encyclopædic Dictionary of Robert Hunter, circa 1885.
It does not appear that the two terms have the same etymological root, but they both have an origin of imitative nature as suggested by An Etymological Dictionary of the English Language Di Walter W. Skeat
derives from whistle from Old English hwistlan, hwistlian (“to whistle”), from Proto-Germanic *hwistlōną (“to make a hissing sound”) from PIE *kwei- "to hiss, whistle," imitative.
Lisp:
from Old English wlisp, wlips (“stammering, lisping”, adj), from Proto-Germanic *wlispaz (“lisping”), from Proto-Indo-European *wlis-, *wleys- (“rod”), from *wel- (“to turn, roll”)
(Witionary)
