“Palangi, the usual Malay word for the rainbow, means ‘striped’. The name varies, however, in different localities. In Perak, it is called palangi minum (from a belief that it is the path by which spirits descend to the earth to drink), while in Penang it is known as ular danu (‘the snake danu’). In Perak, a rainbow which stretches in an arch across the sky is called bantal (‘ the pillow ‘), for some reason that I have been unable to ascertain.
“When only a small portion of a rainbow is visible, which seems to touch the earth, it is called tunggul, and if this is seen at some particular point of the compass the west, I think it betokens, the Perak Malays say, the approaching death of a Raja.
“Another popular belief is that the ends of the rainbow rest upon the earth, and that if one could dig at the exact spot covered by one end of it, an untold treasure would be found there. Unfortunately, no one can ever arrive at the place.”
Source: Skeat, Walter William. MALAY MAGIC being AN INTRODUCTION TO THE FOLKLORE AND POPULAR RELIGION OF THE MALAY PENINSULA. McMillan & Co. London. 1900