The One-time programmable (OTP) refers to a storage area which is only writable once. It is used on various Nintendo consoles to store console-unique information and is written during the factory process.
The Nintendo Wii stores a small amount of data here; some of it is Wii-specific (such as NAND keys), but the hash of the version of boot1 used in that Wii is also stored (making boot1 impossible to update) and the common key used in the Wii.
The following things are stored inside the OTP:
|a-11||NG private key|
|11-15||NAND HMAC (overlaps with NG private key)|