Billabong, as you may have recognized, is a famous clothing brand. It advertises the versatility of fashion even in the corners of the world --- the ocean. Ironically, its purpose wasn't of full appreciation until 1898 where surfing was first introduced to the Americans by the Hawaiians during the forced overthrow of the Hawaiian monarchy, making Hawaii the 50th state in the 20th century. Surfing's progression spread like a virus, across the ocean to California and beyond. The once tradition of the Hawaiians turned into a well-loved, sexy sport. Its popularity opened many doors for businessmen.
Most importantly, the fashion industry.
Gordon Merchant, founder of Billabong, took this right-infront-of-your-eyes opportunity and brought to us BILLABONG in 1973. Being a public company, Billabong, co-handled by the ASX (Australian Securities Exchange), sells various surf and skatebord accesories. The wide range of brand partnerships such as Palmers Surf, Honolua Surf, Von Zipper, Kustom, Nixon, Xcel Wetsuits, and Tigerlily brought Billabong to a whopping $1.0 billion AUD revenue every year!! (statistics of 2006) Billabong surely did make a name for itself.
The history of the name BILLABONG had its ups and downs in the Austral English: A Dictionary of Australian Words. There were several debates and arguments as to which is the most credible and suitable definition for this staggering mystery of its word origin.
With that, russojosh69 must investigate.
(national geographic them song)
Billabong is consists of two parts: billa and bong. Billa is a native word that came to mean as a creek or river by which, it specifically means "transference to water". Coincidentally, the word billa came also into the language of australians, --billa (suffix), meaning, a creek. The word bong or bung (to go bung) meant, literally, to die. So, connecting the two (2) words, BILLABONG connotes a portion of a river that is no longer running. 
That's why the logo (above) explains it all. The two (2) waves signifies the water that is stagnant and motionless. Come to think of it, the brilliance of Mr. Gordon Merchant was explained. He simply meant BILLABONG as a situation wherein water stops temporarily so that surfers can surf smoothly, flaunting billabong merchandise, of course!
Well, there you go. Third mystery solved by your trustee, russojosh69. 
hehe if people know this they wont ask themselves why it is named that way. I even wondered what it was before and now I know. Thanks for the info russ 