A sharp brief rise above the usual. Also a small exploratory build made to learn rather than to keep.
Old Norse spik (a splinter), with related Middle Dutch and Low German words carrying the sense of a large nail, reinforced in English by Latin spica (an ear of grain, a point); a sudden narrow rise takes the same shape as the physical point.
A sharp brief rise above the usual, or a small build made only to learn something before it is set aside. Both take their shape from the same old word for a narrow point.