Who was the old man?

[Ibrîniðilpathânezel]

Saruman may not have been into the use of poisons on his enemies, but apparently, Grima was. At the very beginning of "The Battles of the Fords of Isen" in UT, Tolkien writes:

The chief obstacles to an easy conquest of Rohan by Saruman were Theodred and Eomer: they were vigorous men, devoted to the King, and high in his affections, as his only son and sister-son; and they did all that they could to thwart the influence over him that Grima had gained when the King's health began to fail. This occurred early in the year 3014, when Theoden was sixty-six; his malady may thus have been due to natural causes, though the Rohirrim commonly lived till near or beyond their eightieth year. But it may well have been induced or increased by subtle poisons, administered by Grima. In any case Theoden's sense of weakness and dependence on Grima was largely due to the cunning and skill of this evil counsellor's suggestions.

I wasn't looking for that, but happened to be collecting books scattered around the house and came upon my old beater copy of UT, which, of course, I had to leaf through. That passage just happened to catch my eye; make of it what you will.