B2N2,
Several reasons;
- Same concept as R2D2 (which was already taken)
- Modification of BN2 which is the Britten Islander on which I've flown as a little kid.
- If you say it fast it sounds like Swahili
- BN were my initials in my military ATC days (90-ies)
Every phonecall you made with ATC was finished with your initials.
You would write down the initials of the party spoken to in case of a c@ck-up the guilty party (me,usually) could be easily traced.