Is it farther or further?
1910s, from Tagalog bundok "mountain." Adopted by occupying American soldiers in the Philippines for "remote and wild place." Reinforced or re-adopted during World War II. Hence, also boondockers "shoes suited for rough terrain," originally (1944) U.S. services slang word for field boots.
Remote places; rural regions: The people out there in the boonies may not know you're past it
[Marine Corps 1900+; fr Tagalog bundok, ''mountain'']