Verbs that are designated to a specific limb – like ולקח ונתן (take/give) to the hand, דרך רמס הלך (walk on/trample/walk) to the foot, פנה (turn) to countenance - with all of these, the verb must act with that limb. And this explains why the special verbs (like חפן קמץ כרע) are derived from the name of the limb in which the verb acts.

But for verbs that teach about the action of a certain thing, like זרק שפך חלץ כסה, it is not resolved as to what performs the action and we always learn this from the context and from the verb that is next to it.

For example, the verbכרע*, which means kneel, is derived from the nounכרע, which means knee, as one kneels with one’s knee. And the verbקמץ, which means grasp a handful of something, is derived from the nounקמץ, which means handful. And the verbחפן, which means to take a handful, is derived from the nounחפן, which means handful.*