I a am going to have a go at this from the point of view of ancient Greek and history and I know Βασιλική will be able to correct my basic Greek knowledge.
He was Philip II and 'ίππος' was I believe the ancient Greek word for horse (not sure what the modern word is!) I think maybe in the colloquial it might have meant, as applied to him, 'lover of horses' - but I am not sure if I am on the right track here!
Certainly 'ίππος' remains in the language still as in Hippopotamus (potamus meaning river) so river horse. Sorry I digress!
Someone please tell me - does the first part of φιλιππος mean 'friend' (of horses) or just Philip?
Wish I had never started - help please!