Verifying quote: "My Son Hath Many Heads"
The Scottish warlord Sorley Boy MacDonnell was brought to Dublin in 1586 to negotiate a peace settlement with Elizabeth I's government.
An official pointed to the severed head of MacDonnell's son, nailed above the gateway of Dublin Castle. MacDonnell said: "My Son Hath Many Heads".
It's in the old DNB, but I can't trace the quote back to its root, so I'm hoping for assistance.
I tried Clan Donald resources, but my best effort is a history from the 1870s (p.187): "The grief-stricken old man, groaning in spirit, proudly replied My son hath many heads! The knowledge of this striking incident is preserved in a Macdonnell manuscript"