Actually - what did the phrase really mean? I've just tried translating it on the assumption that it was Italian - or Spanish - or Portuguese - and I seem to be stumped, or at least the computer is.
I think it's the start of a blank verse poem, chastising a child for having too wild an imagination, and implying the consequences will be grave. I feel like it's been written already - maybe it's something I should work on.
[Breadmaster] It came from the Oxford Dictionary of Quotations. To summarise their explanation, on seeing Raphael's St Cecilia at Bologna, c.1525, Antonio Allegri Correggio is supposed to have exclaimed, "Son pittore ancor io!" meaning, "I, too, am a painter!"
On the other hand, he may just have seen through the window that Io had broken loose from its orbit and was hurtling towards the Earth. In a blind panic, he screamed, "For pity's sake, child, tie down the moons of Jupiter!"