'non-' originates from Latin, specifically the word 'non', where 'non' meant 'not'. 'reroutable' is formed from the prefix 're-' (from Latin 're-' meaning 'back' or 'again') plus 'route' (see below) with the adjectival suffix '-able'.

'route' changed from Old French 'route' (meaning 'way, path') and has earlier connections to Late Latin forms related to 'rupta [via]' (literally 'broken [way]') from Latin 'rumpere' to break; 'reroute' is a modern English formation from 're-' + 'route', and 'reroutable' is formed by adding '-able'. 'non-reroutable' is thus a modern negative compound formed by prefixing 'non-' to 'reroutable'.

Initially, components like 'route' referred to a physical 'way' or 'road'; over time, 'route' and derived verbs like 'reroute' broadened to mean any path, course, or data/traffic path. 'Non-reroutable' therefore evolved as a technical adjective meaning 'cannot be redirected', primarily in networking/transport contexts.