I don’t think that it is military or even a boot knife. There were some knives called “Graben Dolch “ (trench dagger) in first World War. (picture enclosed) Please observe the difference of the blade, which is more shaped like a dagger, not a knife.
IMHO your knife belongs to the traditional Bavarian costume, these kind of knifes are designed to be decorative, with relatively big haft (sometimes even containing a small flask for snuff tobacco. They are called “Lederhosenmesser” (leather trousers knife)
They are still produced today, but your example could date back to the 1930’s or 40’s.
A link to a producer of these knifes:
http://www.boellerkaiser.de/Bollersh...er/messer.html
or:
http://members.aon.at/hirschhornschnitzer/messer.htm