Originally, it was a somewhat common mispelling of the word "brother", often by baby boomers, people attempting to imitate Hulk Hogan, and Fudds. It's now used often to troll people, and is used as a mild joke when shitting on boomers in gun communities, and biker communities. It's also especially popular on /k/, other boards of 4chan, when adding complete silliness to a post.
Boomer: do yuo like the 1911??/? IT won 2 worl wards shooting God's own caliber!
Normal Person: It's a decent weapon.
Boomer: AW HE'LL YEAH BORTHER!
Heck yeah borther: a phrase that started on YouTube, under the gaming channels Kryoz and SMii7Y. It’s more common on Kryoz’ channel, but is still often prevalent on SMii7Y’s, as well. It’s spoken in a southern accent, a simple mispronunciation of “heck yeah brother.” This phrase is a definite fan favorite.
Short-hand for the word floccinaucinihilipilification, meaning the estimation of something as valueless (encountered mainly as an example of one of the longest words in the English language).
Precedes or follows either a gratuitously disrespectful or honest remark, originated in New York City. Used in similar fashion to "no offense" or "to be honest," interchangeably.
Ya mans is wild buns, respectfully. Respectfully he's washed.
After school, The Modells on Jamaica Ave was active. Respectfully.