The spelling Atholl is more frequent as a placename in Scotland. This is the spelling of the main district in the highlands and the historical Earldom. I think Athol is more common as a surname, and hence I would say that the first name in this spelling is more likely to have come from the surname rather than the place name.
Athol is the given name of the protagonist in Graeme Aitken's novel for teens 'Fifty Ways of Saying Fabulous.' Athol is embarrassed of his name and goes exclusively by Billy Boy.
This is the name of my town. The LS Starrett Company has its main offices here. Athol was named after Blair-Atholl, Scotland--periodically, we are visited by the Duke of Atholl.
I actually believe that this has an oddly handsome hue to it... Unfortunately it has been tainted unusable in most English-speaking countries (especially the United States). The explanation? "Athol" resembles a certain crude "term" for someone's rear-end. "Ahth-ol.. Ath-ol.. Ath-hole," if you understand. Whether or not the mature generation interprets it as so-- school-grade children are merciless, and this should be seriously taken into consideration before you make a written-in-stone decision to dub your son.