Matt Jefferies, who was a pilot, came up with the NCC registry as a variation on the N-numbers on aircraft.
As Jefferies put it:
According to Jefferies, 1701 was supposed to mean seventeenth starship design, first build.
That however wasn't followed up in the actual show or the series that came after.
As Jefferies put it:
“I wanted a very simple number that could be spotted quickly. You’d have to eliminate 3, 6, 8, and 9, so I just went for 1701, which incidentally and coincidentally, happens to be very close to the license number on my airplane — NC-17740. But I have never really stepped out and squashed the rumor that the number on the Enterprise came off my airplane.”
Source: http://forgottentrek.com/designing-the-first-enterprise/
According to Jefferies, 1701 was supposed to mean seventeenth starship design, first build.
That however wasn't followed up in the actual show or the series that came after.