I think you will find that the irregular verbs are Germanic in origin.
They are; however, they go back further than that, to the ancestral Indo-European language. At that time vowel changes, such as those in many irregular verbs (sing-sang-sung) were one of the methods of choice for word formation - so they were not irregular, but regular. (European philologists gave this the name Ablaut, if this helps people find more information.)
Enough patterns survived to give "subregularities" rather than just irregularity (method in madness, so to speak). More in Old English and German than Modern English, but there are still patterns like sing-sang-sung which are common enough to be of some help to English learners.
I don't mean that this applies to all English irregular verbs. Other processes have been at work as well. But I hope this helps.