Dutch words ending on a long vowel (such as loempia (spring roll)) get an apostrophe for the plural, so mr. Tran has the correct spelling.

Loempia is originally a Chinese word (潤餅) from the Min Nan dialect. From the Chinese it entered the Malay language and Indonesian. From there it was introduced in the Dutch language. We write it with a "oe", but in modern Indonesian it is written "lumpia". The oe is pronounced like "oo" in "moon".

Apparantly 潤餅 is pronounced "Lun Pia". In my Dutch dictionary it says that 潤 can also mean decorate and 餅 also pancake, so decorated pancake. Why the Vietnamese and Malay took over this word it doesn't say. Maybe Chinese from Fujian province settled in Vietnam and Malaysia and made the spring rolls.

Now you know that loempia isn't a nasty Vietnamese disease. You can buy loempia's at a lot of places, they are typically around €1 a piece.