Engineering is any art where one is designing and constructing.
The classic definition of the word engineering is:
The art of managing engines.
Later, the word engineering took on an additional meaning:
The art of directing the artillery of an army.
Designing and Constructing
And still later, the word engineering came to mean:
Any art where one is designing and constructing.
This definition of the word engineering (designing and constructing) is the one that is most common today.
Software engineering is the art of designing and constructing software.