While researching Q: What is the Role of "iste" in These Quotes from Cicero?, I came across this line in Cicero's "Epistulae ad Atticum 15.20.3":
Pompeium Carteia receptum scribis; iam igitur contra hunc exercitum. utra ergo castra? media enim tollit Antonius. illa infirma, haec nefaria. properemus igitur. sed iuva me consilio, Brundisione an Puteolis. Brutus quidem subito sed sapienter. πάσχω τι. quando enim illum? sed humana ferenda. tu ipse eum videre non potes. di illi mortuo qui umquam Buthrotum! sed acta missa; videamus quae agenda sint.
This is translated on Perseus (E.S. Shuckburgh, 1908):
You say that Pompeius has been received at Carteia, so we shall presently see an army sent against him. Which camp am I to join then? For Antony makes neutrality impossible. The one is weak, the other criminal. Let us make haste therefore. But help me to make up my mind-Brundisium or Puteoli? Brutus for his part is starting somewhat suddenly, but wisely. I feel it a good deal, for when shall I see him again. But such is life. Even you cannot see him. Heaven confound that dead man for ever meddling with Buthrotum! But let us leave the past. Let us look to what there is to do. !".
The attitude of Cicero, towards Buthrotum (and those who would work against it) is clear from his comments to Dolabella in Cic. ad Att. 15.14.3:
"quod reliquum est, Buthrotiam (neuter accusative?) a et causam et civitatem, quamquam a te constituta est (beneficia autem nostra tueri solemus), tamen velim receptam in fidem tuam a meque etiam atque etiam tibi commendatum auctoritate et auxilio tuo tectam velis esse. satis erit in perpetuum Buthrotis praesidi magnaque cura et sollictudine Attrium et me liberaris, si hoc honoris mei causa suscerperis ut eos semper a te defensos velis. quod ut facias te vehementer etiam atque etiam rogo." =
"For the rest, though the claims and political existence of the Buthrotians have been set on a firm foundation by you (Dolabella), I would wish you--for I always want to make my favours secure--to resolve that, having been taken under your care and frequently recommended by me, they shall continue to enjoy the support of your influence and active assistance. That will be sufficient protection for the Buthrotians forever, and you will have set both Atticus and myself free from great care and anxiety if you undertake in compliment to me to resolve that they shall always enjoy your defence. I warmly and repeatedly entreat you to do so."
Returning to the main point:
"di illi qui mortuo umquam Buthrotum!"
"Literally: These gods who--to/for/by/with/from a dead man--ever--Buthrotum.
Assuming that "Buthrotum" is a neuter accusative, then a sense of "directed towards" may be invoked; though, shouldn't preposition, "ad", be present?
This improvement does not tell me that the gods should, or did, confound the dead man; or, that he, the dead man, ever meddled with Buthrotum.
What's going on, here?
When Cicero wasn't invoking the gods to confound someone, he used more conventional Latin:
Lucio Antonio male sit si quidem Buthrotis molestus est!" (Cic. de Att. 15.15.1) =
"Confound Lucius Antonius (brother of Mark Antony) if he makes himself troublesome to the Buthrotians!"