It is a myth that engineer originated to describe those who built engines. In fact, the words engine and engineer (as well as ingenious) developed in parallel from the Latin root ingeniosus, meaning "skilled". An engineer is thus a clever, practical, problem solver. The spelling of engineer was later influenced by back-formation from engine. The term later evolved to include all fields where the skills of application of the scientific method are used. In some other languages, such as Arabic, the word for "engineering" also means "geometry".
The fields that became what we now call engineering were known as the mechanic arts in the 19th century.