Optus abuses the Naked Broadband term
Since ADSL has been available, an active copper analogue PSTN (Plain Switched Telephone Network) line was required to be connected. ADSL uses frequencies higher than normal speech to transfer data across the telephone line. Filters are installed to prevent these frequencies from reaching equipment used for speech and fax transmissions (i.e. telephones and fax machines).
In 2007, a new movement in the internet service provider industry started to offer ADSL connections without the need to pay for telephone line rental (usually from Telstra). At the time, fixed telephone lines were starting to fall out of favour due to the increasing takeup of mobile phones. The ISP would essentially 'rent' the telephone line from Telstra, and build the rental price (which is discounted) into the monthly subscription fee for the ADSL connection. This proved to be an attractive solution to those who had no need to rent a fixed landline but still had a desire for fast internet access.
The phone line itself could then have the telephone service removed (i.e. no dialtone), and its only purpose would be to carry the ADSL signal between the customer's modem and the telephone exhange. The term 'Naked ADSL' was thus coined, to differentiate between ADSL plans that required an 'active' phone line and those that didn't. A number of ADSL ISPs, such as iiNet, TPG, etc started to offer Naked ADSL plans, which were distinct to their other plans which required an active phone line.
In the past, optus had a tradition of offering discounts to bundled products, such as their telephone and cable internet plans. As they have their own Hybrid Fibre Coaxial network, they didn't normally need to rely on the Telstra copper network to provide broadband. Instead, they provided high speed internet connections via the cable TV infrastructure.
In 2009, Optus started to take notice of the 'Naked' term more, and decided to start branding some of their products as 'Naked', often erraneously. The abuse of this term was used to describe products that were originally offered as 'standalone', meaning they were not bundled with another product.
The reason why this usage is erraneous is because their internet access products either don't need a telstra copper line (such as Optusnet Cable), or rely on the customer already having an active (believe it or not) Telstra phone line!
The abuse is worse when they use it to describe their standalone cable internet products. Firstly, cable internet never requires a phone line. And the term 'Naked' is only applicable to ADSL that uses a copper telephone line with no dialtone!
Granted, they do use the word "Standalone" in brackets in some places, however their marketing completely warps the idea of proper a "Naked" ADSL connection. It makes no mention of how their ADSL plans can be connected to a phone line with no voice service.