Actually, it dates back to what an Engineer was. Being an ex Royal Engineer, this was all part of our training. An 'Engineer' was someone who built 'Engines of War' or Siege Engines (back beyond Roman times). Romans went to war, and took Engineers with them to build their engines of war, bridges, roads, catapaults, drainage, sewers etc.. Thats why they were so succesful.
Therefore a 'Civil Engineer' works on 'non-military' but civilian projects, hence why we have Civil Engineering. Civil Engineer is now recognised far more than the original 'War Engineer', but it is called Civil because it is derived from civilian (both person and nature of project) not because of our bedside manner.