An Etymological Dictionary of the German Language/Annotated/lispeln

by Friedrich Kluge

lispeln, verb, ‘to lisp,’ with a diminutive or frequentative suffix from Middle High German and Old High German lispen, verb, ‘to stammer’; never ‘to speak through the lips’ as a derivative of Lefze (see Lippe); it rather represents wlispen (thus in Lower Rhenish in the 15th century, also by transposition, wilspen?). Compare Anglo-Saxon wlisp, wlips, Old High German lisp, ‘stammering’; English to lisp, Dutch lispen.