Why this branch of engineering is called 'civil engineering'?
To talk about Civil Engineer, first we should know how ENGINEER has came. Because, Civil Engineering is the oldest branch of engineering after military engineering.
The intended meaning of the word ENGINEER is not the same as when it has originated. The word ENGINE is derived from Latin word “ingeniare”.
The word engineer was initially used in the context of warfare, dating back to 1325 when engine’er (literally, one who operates an engine) referred to "a constructor of military engines". In this context, "engine" referred to a military machine, i. e., a mechanical contraption used in war (for example, a catapult).
Until late 18th century, there is no disparity between military and civil engineering. Both are just ENGINEERS. The first self-proclaimed civil engineer was John Smeaton, who constructed the Eddystone Lighthouse.