In any depiction of multiple national flags, you’ll notice that all of them are rectangular or occasionally square, except Nepal’s oddball double pennant. Why does Nepal have so weird of a flag?
Flag of Nepal - Wikipedia gives some of the history of their flag.
I’d guess the answer is half that they intentionally wanted a flag that stands out to emphasize their uniqueness, and half that they’re generally less influenced by the major European naval powers than most countries.
Because they didn’t bow to the pressure of conformity. There’s nothing inherently correct about having a rectangular flag, and we still fly variations like pennants and swallowtails, but the rectangular flag is simple, has plenty of room for designs, looks good both horizontally and vertically and thus became the pattern for the national flags in Europe. The rest of the world then followed suit. Except for Nepal who had a different tradition and stuck with it:
Basically, it’s a merger of two individual pennant flags. Note that the two pennants are actually different in shape – the one on bottom has a sharper angle. There’s lots more on this at Flags of the World: Nepal
I believe that text was written in the 90s, so they would have been first joined in the 19th century.
http://flagspot.net/images/n/np_gatel.jpg
http://t3.gstatic.com/images?q=tbn:vKE3BMgrNU53wM:http://66.70.224.3/PhotosD1/BDSC-015-14.jpg&t=1
Many temples in Nepal have and still do fly pendent shaped flags as a display of their particular denomination. This is true for both Buddhist and Hindu temples. Pre-independence if a pendent was flown that was made up of two combined pendants it was a temple that served both religions. Although rare it was seen as a symbol of the unity of the two major religions of the country thus inspiring the flag.
The shared temples are for the most part non existent today.