The word Hyperpedia is derived from the Greek hyper- signifying over, excessive, more than normal; and -pedia, which is from the Greek paideia meaning education (as in encyclopedia).
It can be thought of as a contraction of hypertext encyclopedia, hypertext being the name given to interactive pages with hyperlinks found on the internet. It also rhymes with hypermedia, an alternative name for the content found on the internet.
Hyper- is one of the few combining forms in English that is derived from Greek - most are from Latin, and only clumsy words such as television mix Greek and Latin roots. Perhaps this prefix is appropriate, as these pages are likely to go into the topics on them in far more detail than most people really want to know!
The spelling without the 'a' was chosen as it appears more modern, and besides, my old computer only allowed directory names of up to 10 characters, so hyperpaedia would have been too long!
I'm sure the word isn't unique, but if it is in use elsewhere, I did invent it independently!