Most wooden hand planes body are solid thickness from front to back. But a few breads out there have the material of the body relieved or narrowed from the middle section to the back.
These types of hand planes are called Razee Planes.
The term razee is believed to come from the french word past tense word for razor. vaisseau rasé The story of the design seems to have come from the wooden ships of the time. Not by the French, as the word first implies, but by the British. The British in 1570 made ships of a “race-built” design. This design gave it a sleek look. It also was a way to improve the warships too. By removing the upper decks they now could reduce weight making the ship lighter and more manageable to move. It also allowed movement for gun canon placement.
So did a ship builder design the lower sleek look of the razee plane? No one really knows for sure. But razee planes seems to work and feel better in use than the solid body design. The narrowed section allows the tote (handle) to be lower so that the thrust pushed by you hand is squarely behind the stock. This gives better balance and control. On a standard solid body plane, the thrust is above the body of the plane.
Razee planes mostly come in the form of jack planes (15 inches long) and fore planes(22 inches long). They are not rare but are not common either. I have razee jointer plane (26 inches long) which might be considered rare by some.
Whether it was the French, or the British who designed it, we may never be know. But one things is for sure, it works GREAT! I use my razee jointer plane quite often. And when it makes beautifully thin curled shavings, well, it just makes me want to dance with joy.