कप य

14.6.26
The initial decipher made me think that क is hand/hold/stone and प is legs/rope.
As we go deeper, I find that that is later date developement and originally both क and प have largely interchangeable use - at least as luimb. Lot of sea shore movements are referred to with क. That would not have been hand movements but leg movements.
My current hypothesis is - both क and प are two different types of movement. Originally both types of movements can be performed by both type of limbs - upper and lower.
Evolution and teaching of language started while upper and lower limbs were capable of both क and प type of movements.

Later developments indicate क type of movements are primarily hand based and प type of movements are primarily foot based.

क is brachiation and consecutive manipulative use of limbs - reaching grasping.
प is locomotor / postural and leaping use of limbs - propulsion, power.
Both क प achieve य. Both set of limbs could be used for both functions when language emerged. Later it got specialized and क got more and more associated with hands and प with legs. But at time of emergence of धातु पाठ and teaching of very initial सुत्र - the use was not exclusive. 3.1.13 refers to manipulative use of leg figures while referring to leg as क and leg fingers as क्यष्. Though what the sutra instructs can be done by Sapiense anatomy also, in sapiens context it would have been called प्यष् and not क्यष्. So either it was possible to use legs for manipulative use or language had रूढ memory of that use