'walk-in' originates from the English words 'walk' and 'in', where 'walk' meant 'to move on foot' and 'in' meant 'inside'.

'walk-in' was initially used to describe spaces like closets or freezers that one could physically walk into, and later evolved to describe services that do not require appointments.

Initially, it meant 'a space one can walk into', but over time it evolved to include services that do not require prior arrangements.