Lately I stumbled upon an email signature in which the author had entitled their job "Principle Engineer". As it has never been explicitly clarified, I suspect this is a homonym of the intended adjective. That is, unless his job was to maintain the moral upstanding of the company.
Of course, a "Principal Engineer" ought to be the first in order of importance [Cambridge Dictionaries Online], which is also not true as there are, possibly, hundreds of employees in his company with this designation.
Josh's Space 