Graeme Skinner (in the booklet notes) with CD, TP (Tall Poppies) 009
Mozart:  Unexpurgated Scatological and Other Songs, Canons and Piano
Variations", suggests scatology was a subject of Mozart secret family
language.  He sites a letter (January 1778) of WAM to his mother:  "I'll
keep the Concerto for Paris, it's more fitting To scribble it down there
one day when I'm shitting." Another from 56 year old Frau Mozart to
husband, Leopold:  "Best wishes, my beau, and lick your backside so.  Good
night, dear, but first you must shit in your bed and make it bust" (1977).
>From memory of my childhood it would seem that humor in such vein is
commonplace in German families and has absolutely nothing to do with
lifestyle or stature achieved.

Norman