The expression was introduced to English by American military personnel serving in the Philippines during the early years of the 20th century. It derives from the Tagalog word "bundok", meaning "mountain".
Boondocks, or diminutively, "the boonies" has since evolved into a more general American slang term for "the country" or any rural/wilderness location in general, regardless of topography or vegetation, that is isolated. The diminutive "the boonies" can be heard in films about the Vietnam War such as Casualties of War by Brian De Palma. It is used by American military personnel to designate Vietnam.
Among synonyms for "the boondocks" is "the sticks".
"Down In The Boondocks" was a song written & produced by Joe South and sung by Billy Joe Royal. It was a hit in 1965, reaching #6 on the Cash Box magazine chart and #9 on the Billboard Hot 100 chart. In the UK, it hit #38 on the Record Retailer chart.