I.up [美 əp, 英 ʌp]副up often appears as the second element of certain verb structures in English (back up, pick up, sit up, etc). For translations, see the relevant verb entry (back, pick, sit, etc).
And it is possible for individuals with desktop publishing skills and access to templates or photographs of real degree certificates to knock up their own convincing fake versions.
I think there'll always be people who find it individual and personal to them, as something they can knock up quick while potentially creating hook ups with other artists.
See, we can all knock up dinner but keeping those trays coming with a smile three times a day with love and nourishment unsaid but clearly there -- that's the challenge.