late, delayed, winter radical (no. 34)
夂 centers on the idea of lateness or delay, often associated with the end of a season like winter. As a radical, it represents the winter concept used in other characters.
夂 is a pictograph of a foot pointing downward, symbolizing the end of a journey or lateness. It is also used as a radical for winter, likely from the idea of the year's end.
The shape looks like a foot stepping down, as if arriving late after a long walk. Think of winter as the late season when the year's journey ends.
For チ, imagine a late train arriving with a loud 'chee' sound from its whistle: chee -> チ, and the train is delayed.