I just recently realized that "Dr. Noonian Soong" and "Khan Noonien Singh" sound familiar. Is there documented confirmation that the TNG writers were inspired by Star Trek II? Or is this purely a coincidence?
Directly - no.
They were both named after Kim Noonien Singh, who Gene Roddenberry knew during World War II.
Additional trivia from IMDB:
Roddenberry also had a tendency to reuse names - for example, Dylan Hunt was used several times.
Sorry to be tardy to the party,
But Dr. Noonian Soong is in fact linked to Kahn. Dr. Soong's great grandfather Arik Soong created the Augments (the super beings led by Kahn) and played a vital role in the Eugenics Wars. Khan's name is a bastardisation of Soong's name, but Kahn is (in a weird kind of way) Noonian Soong's great great uncle.
I just finished watching Star Trek Enterprise S04E04-06 and it's about Dr. Noonian Soong. He was in prison for crossing the line when he was on the project creating the genetic supermen, the same as Kahn. The episodes also have Dr. Noonian Soong's children, not his literal children but a group of kids he raised that were genetic supermen. He stole the embryos when he was working on the project.
At the very end of ep6 Dr. Noonian Soong expresses his interest in making an android....... Inception of Data ;-)
Interestingly, one of the supermen children made mention of rumors of the ship "Botany Bay" (the ship that carried Khan and his crew) and Khan but Dr. Noonian Soong dismissed it as not being true.
So they are not directly linked but thought it would be interesting to mention this.