Daniel Tenofsky was a name used by Jacob Deiter, a failed law student who managed to fake his way to the position of ADA in the Manhattan District Attorney's Office. (L&O: Nowhere Man)
History
The choice of name was based on another man named Daniel Tenofskie, (note the spelling) who attended the Arizona university where Deiter worked and whose personal information he stole and used to fabricate his legal credentials.
He claimed to have attended Brooklyn Law School, and then worked on trials in the DA's office. Later, he moved to the Appeals bureau. It was later revealed that he did so to avoid dealing with two members of the Masucci Crime Family.
He was regarded by fellow attorneys such as Jack McCoy as an excellent attorney of high character, if having a minimal social life. Due to the quality of his work, no one bothered to check the accuracy of his credentials until his death revealed that he was not who he claimed to be. His alias was exposed as such when it was discovered he was in Phoenix at the same time he was supposedly attending law school in Brooklyn.