The phrase comes from northern rural Vietnamese, especially before the 1950s, when corn was a common staple and easily observable in daily life.

Corn kernels (after boiling or stripping the husk) are soft, smooth, and very pale, almost milky-white or ivory-white.

Villagers used it as a visual metaphor for very light skin, especially babies or women who avoided sun exposure.

So “trắng như bắp” originally simply meant:

**"as white as corn kernels" → very pale."

It did not refer to foreigners at first.

✅ 2. How the meaning shifted

After the 1990s, Vietnam opened up more to foreigners (tourists, NGOs, English teachers).

People noticed that Westerners, especially northern Europeans, tended to be:

lighter-skinned than Vietnamese

easily sunburned

visibly “trắng như bắp”

Because of this, some younger Vietnamese started jokingly using “bắp” or “da bắp” in private jokes to refer to extremely pale white tourists or expats.

This was never a mainstream label — more like:

internet memes

teenagers teasing each other

inside jokes like “trắng như bắp Tây”

(http://www.autoadmit.com/thread.php?thread_id=5794265&forum_id=2Elisa#49407411)