What is the full official name Doctor Noonien Soong gave to his android (known in ST: TNG as "Data")?
Is the entire name simply Data, or is it an acronym?
In the second season episode "The Measure of a Man", Riker pulls up Data's schematics on a wall monitor. On the lower right of the display, we see "LT CDR NFN/NMI DATA" which should be read as "Lieutenant Commander No First Name No Middle Initial Data."
Also from Measure Of A Man, this is Data's full name as shown by the Enterprise computer (to Cmdr. Riker): Lt. Cmdr. NFN NMI Data. Spelled out, this becomes: Lieutenant Commander "No First Name" "No Middle Initial" Data.
According to StarTrek.com database his full name was simply Data.
I don't recall hearing or reading about the origin of the name but it always sounded right :)
Data was initially a nickname given to him by Starfleet personnel. Data did not recall his life prior to being metaphysically born again by being turned on after a memory wipe. Thus, to the OP's question, we don't know what Doctor Soong named him. We can presume he was given a first name, because Lore had a first name. It's a compelling thing to wonder if Data ever considered adopted the surname Soong in some fashion.
I appreciate the challenge below to back up my answer. It would seem I was partially correct; Data chose his own name.
EPISODE: Datalore S01E14
TASHA: You were just lying out there in the open? No identity record, no instructions?
DATA: Only a layer of dust.
RIKER: What's the first thing you remember, Data?
DATA: Opening my eyes. Looking into the eyes of the Tripoli landing party. They believed that the signal device sensed their presence and activated me.
In the prologue to the novel adaptation for Encounter at Farpoint by David Gerrold, Data chose his own name, due to his love for, and identification with, knowledge.