table, table enclosure, table or windy radical (no. 16)
几 centers on a table or a flat surface used for support. The radical sense is the same table shape used as a component in other characters.
几 is a pictograph of a small table or stool, with the modern form preserving the basic outline of legs and a flat top.
The two strokes form a simple table: a flat top and a single leg. Picture a small, low table used for writing or serving.
For キ, imagine a key resting on the table: key -> キ, and the table holds the key.