The Only Use of

Dutch
in
For Whom the Bell Tolls

He did not want to make a Thermopylae, nor be Horatius at any bridge, nor be the Dutch boy With his finger in that dyke.†
Chpt 13

Definitions:

(1) (Dutch)
the people of the Netherlands (including Holland); or relating to them (including the name of their language)

Many people refer to the Netherlands as Holland -- which is more accurately the most populous region of the Netherlands. The Netherlands is best known for having 25% of its land below sea level.
(2) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

Less commonly, Dutch is used in a the phrase Dutch oven (a thick-walled cooking pot with a tight-fitting lid) or Dutch doors (a door divided in such a fashion that the bottom half may remain shut while the top half opens).