'unmoorable' originates from English, specifically the elements 'un-' + 'moor' + '-able', where 'un-' meant 'not', 'moor' meant 'to secure (a vessel)', and '-able' meant 'capable of'.

'moor' changed from Old English (verb) 'mōrian' (or similar early forms) into Middle English forms such as 'moren' and eventually became the modern English 'moor'; the adjectival suffix '-able' (from Latin '-abilis' via Old French) formed 'moorable', and the prefix 'un-' produced 'unmoorable'.

Initially, 'moor' meant 'to secure a vessel'; combined with '-able' it came to mean 'capable of being moored', and with the prefix 'un-' it now denotes 'not capable of being moored' (the literal sense) and by extension 'not able to be settled or secured' (figurative).