Most Malaysians don't know its origins of their semantical affix "lah" for sure. Like most legends whose starting point is often lost in transmission, most people use myths to convey a meaning deeper than the original story, with every generation adding a layer of meaning to the symbol, enriching it with sometimes complex articulations of often simple truths.
Yet for sure, "lah" has something of the legendary about it, akin to the Greek myth of Midas who could turn everything he touched into gold. The "lah" word is the almighty Malaysian hero able to capture all things Malaysians and able to "Malaysianize" everything he touches. Borrowed from the old Malay by the Chinese and Indians who've then taken it into the English language which the three races share, the word "lah" is the bridge between all Malaysians, all things Malaysians and between Malaysians and the rest of the world.
Thus the "lah", used only in this part of the world (Malaysia and Singapore) makes "Manglish" (Malaysian English) very unique and foreigners newly arrived in this country will find it quite baffling at first. Sure, these Malaysians are speaking English but what on earth is that strange musical note that they place at the end of their sentences every so often?
