What is heeling during vessel berthing?

When a vessel berths on a fender system at a pier, the point of contact of the berthing ship may be above or below the centre of gravity of the ship. During the berthing operation, some kinetic energy is dissipated in work done to heel the ship i.e. the work done to bring the ship an angle of heel. This energy is normally a small fraction of total berthing energy and therefore it is normally not considered in design. However, designers should pay attention to the possible hitting of the berthing structure by the vessels in case the contact point is well above water level.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.