Well, it's a bit convoluted but it goes like this...
Ralph is the contracted form of the Old Norse name Radulfer (or its Norman form Radulf). Scandinavian settlers introduced it to England before the Norman conquest, though afterwards it was bolstered by Norman influence. In the Middle Ages it was usually spelled Ralf, but by the 17th century it was most commonly Rafe, reflecting the normal pronunciation. The Ralph spelling appeared in the 18th century.
The nick name Ralf was given to small male children as a term of affection since "Ralf" meant 'being as determined as a wolf'. Since the name was Scandinavian in origin, it was later interchanged with The name Tyke which means 'one who is determined'. 'Tike' is simply a derivative of 'Tyke'.
There you have it!