E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
It was Porson who said he could rhyme on any subject; and being asked to rhyme upon the three Latin gerunds, gave this couplet
When Dido found Æneas would not come,
She mourned in silence, and was Di-do dum(b).
In the old Eton Latin grammar the three gerunds are called -di, -do,
-dum. In modern school primers they are -dum, -di, -do.
When Dido saw Æneas needs must go,
She wept in silence, and was dum(b) Di-do.
E. C. B.
Dido was queen of Carthage, who fell in love with Ænas, driven by a storm to her shores. After abiding awhile at Carthage, he was compelled by Mercury to leave the hospitable queen. Dido, in grief, burnt herself to death on a funeral pile. (Virgil: from Ænid, i. 494 to iii. 650.)