I finally checked online to be sure, and found that my suspicion that I
knew the tree by a different name was correct.  My family, for at least
4 generations, comes from north central Texas, and far eastern Texas (3
generations born in same hospital!).  We've always called the tree a "Bois
d'Arc" (Bois du Arc French for "wood of the bow") and as I recall called
the fruits "horse apples," though I can think of no reason to do so.
Texas A&M lists the name "horse-apple" for the tree, so I must not be
completely nuts for thinking that.  I had never heard of it being used
for insect repelling.  Will have to ask my grandparents.  Some websites
mention the insect repelling, and I also read that squirrels and deer
like to eat them.  More info at:
 
http://www.osageorange.com/ (look for Osage Orange history link halfway
down page for link list)
 
Debra in Fort Worth
[Posted in FML issue 3564]