The pattern repeats every seven letters, so the name ends on the 7^\text{th}, 14^\text{th}, 21^\text{st}, ... letters, i.e. on every multiple of 7.
Since 1000 \div 7 = 142 \text{ r}6, there are 142 complete copies of the name, and then the 1000^\text{th} letter is the sixth letter of the next name. Therefore the 1000^\text{th} letter is \text d.