I was under the (probably mistaken) impression that the term big data originated in the physics community when they needed to deal with experiments that produce petabytes of data per second or more. Volumes that simply couldn't be processed and analysed even by the biggest fastest systems of the time.

To me, it it's not BIG unless it's bigger than normal transactional data, even if you are Boeing and it's your BOM database! For example, looking at several decades of data rather than just the usual 12 to 24 months.