Actually, whereas the word literally means that, the use of the word philosophy to mean a disciplined investigation into questions actually predates even Plato'

Actually, whereas the word literally means that, the use of the word philosophy to mean a disciplined investigation into questions actually predates even Plato's Academy. The reason why academic titles have the word philosophy in them is because modern investigations have developed from the philosophical tradition. For example, philosophers may have a question, "what is value?", or "what is the nature of the world?", born out of the philosophical tradition. Then, after sufficient discussion and philosophical investigation, they figure out that certain methods, approaches to answering these questions, are very fertile and lead to informative answers, e.g. value as a real-valued mathematical measure, or the nature of the world as a generalization of empirical observation. Such methods may prove to be so fertile that you may have academics spending decades or centuries investigating the implications of that method. Hence you have economics and philosophy.