If we can't choose mouthful (which for some reason sounds thematically correct), "chunk" gets my vote. *(Chunk = Maybe not the most technical, but has been working for me all along ...)*
Chunk is at least the proper English term for these bits between the colons. The process of breaking up a long string into shorter substrings is already known as "chunking". With IPv4, the chunking was done on octet boundaries so people used the specific term "octet" instead of the more general "chunk". But in the absence of a specific term, chunk is the correct and proper way to refer to these bits. IPv6 addresses are chunked into 16 bit chunks and each chunk is written down in hexadecimal notation with a colon between the chunks. For example, 805B:2D9D:DC28:0000:0000:FC57:D4C8:1FFF. Of course there are some other rules that allow for shorter strings but they all start with the 8 chunks separated by colons. The last 4 chunks represent the interface identifier and the first 4 chunks are the network prefix. -- Michael Dillon