I didn’t know of that currency until today, either.
I just learned about it from playing around with the currency information service at xe.com, which has Bitcoin added as “XBT”. And they explain their decision to use that code like this:
Bitcoin is not recognized by the ISO and therefore does not have an official ISO 4217 code. A currency code is generally built from the two-digit ISO 3316 country code and a third letter for the currency. Although “BTC” is often used in the Bitcoin community, BT is the country code of Bhutan. An X-code reflects currencies that are used internationally and so, XE has chosen to use XBT to represent Bitcoin.
The Bhutanese Ngultrum has the code of “BTN”, which is the closest of any currency code to “BTC”.
One Nulgtrum is worth considerably less than one bitcoin. The currency is pegged to the Indian rupee. You need 85,742.7 of those to buy one bitcoin right now.
All of this would seem to make Bhutan an excellent candidate for the first country to recognize Bitcoin as an official currency.
I hear their largest export is electricity, from their excellent hydropower resources. The latest power tariff is 1.59 Ngultrum per kWh, which is basically zero. That gives Bhutan an interesting opportunity to attract some bitcoin mining operations.
Crossposted to the Reddit Bitcoin forum here.