'sidetrack' originates from the combination of 'side' and 'track', where 'side' meant 'lateral' and 'track' referred to a path or course.

'sidetrack' evolved from the literal meaning of diverting a train to a side track, eventually becoming a metaphor for diverting attention.

Initially, it meant 'to divert a train to a side track', but over time it evolved into its current meaning of 'diverting attention or focus'.