They used to be made by Sipura - so guessing it comes from that.
From what I understand, a load of disgruntled engineers who made the Cisco ATA186 etc left Cisco to found Sipura, who released various ATAs and then later - phones. Sipura was purchased by Linksys and the SPA range moved to them (SPA9xx etc). Cisco then bought Linksys and launched the small business range, the SPA5xx which is largely the same as the SPA9xx series - but there is Skinny, XML browsers, better screens/tweaked hardware etc.
Some of that is rumour and hearsay - but I think it's roughly right!..
Configure Multicast Paging on the Cisco IP Phone 7800 Series or 8800 Series Multiplatform Phone
The Cisco IP Phone 7800 and 8800 Series Multiplatform Phones provide voice communication over an Internet Protocol (IP) network...
Add Call Park on a Cisco 7800 or 8800 Series Multiplatform Phone Key Expansion Module
Call park allows the user of the phone to put an incoming call on hold so that the call can be retrieved on another phone. A call is park...