Fall Back

The term “to fall back” suggests that one must set the clocks one hour back when Daylight Savings Time ends. It is associated with the fall (autumn) season because the Daylight Savings Time schedule ends in the fall. The fall season and the end of daylight saving time mark a period when the days become darker, in that there are less hours of sunlight during the day, particularly in the afternoons or evenings, as winter soon approaches. 

Ps. This is for UK