Yeah, it is a strange one. If you look at the Spanish guadañar (“to mow”), the root makes more sense. And then there is weidanōn (“to hunt, chase”), which also exhibits the odd ending. Could it be a merging of the two words?
Looks like weidanōn is from the Webster's Seventh New Collegiate Dictionary. http://www.utexas.edu/cola/centers/lrc/ielex/X/P2112.html#OHG