oz in dxb has it correct in one hit, and that's the official words from Boeing.
Eaaasssy does it, particularly when the controls are towards the end of their travel (a control position that would not be used in flight except in the most extreme cases).
For the record, that applies to ALL control surfaces (and probably most aircraft), it's just that the Elevator produces the most noticeable shudder in the aircraft in the B777.
Regards,
Old Smokey