'non-dockable' originates from the productive English combination of the prefix 'non-' (from Latin 'non' meaning 'not') attached to 'dock' and the adjectival suffix '-able' (from Latin '-abilis' via Old French) to mean 'not able to be docked'.

'dock' as a noun/verb comes from Middle English (e.g. 'dok', 'dokke') referring to a place or action of mooring ships; the suffix '-able' derives from Latin '-abilis' through Old French to form adjectives meaning 'able to be ...'; 'non-' is a negating prefix from Latin. These elements combined in modern English into the descriptive compound 'non-dockable'.

Originally the parts separately meant 'not' (non-), 'a place or action of mooring' (dock), and 'capable of' (-able); together they evolved to the current specialized sense 'not capable of being docked'.