Probably because of the word definitions.
gripple
[ grip-uhl ]
adjectiveBritish Dialect.
miserly; avaricious.
grapple
[ grap-uhl ]
verb (used without object),grap·pled, grap·pling.
to hold or make fast to something, as with a grapple.
to use a grapple.
to seize another, or...