'unstreamlined' originates from English, specifically the prefix 'un-' plus the adjective 'streamlined', where 'un-' meant 'not' and 'streamline' meant 'to make smooth in flow or to make efficient/simpler.'

'streamline' is a modern English formation (early 20th century) from 'stream' + 'line' used to describe aerodynamic forms; 'streamlined' (past participle/adjective) was then negated by adding the productive prefix 'un-' to form 'unstreamlined.'

Initially, 'streamline' referred mainly to shaping for smooth flow (especially aerodynamics); over time its sense broadened to 'make more efficient or simpler,' and 'unstreamlined' therefore denotes the absence of those qualities.