Meaning:

“半” is “semi-” and “永久” means “permanent.” This term originally refers to “semi - permanent makeup” or microblading — a popular trend in the world of beauty makeup. The techniques of microblading include treatments such as microfeathering and lip blushes, which takes men and women much less time than going through a usual daily lengthy makeup routine. The technique limits the process to roughly once a year and offers the most natural-looking results.

Now netizens are borrowing this term to everyday situations to refer to items that people always have or things that always happen.

Example:

A: 我忘带口罩了，你能给我一个吗？

Wǒ wàng dài kǒuzhào le, nǐ néng gěi wǒ yīgè ma?

I forgot to bring a mask. Can you give me one?

B: 现在口罩都变成“半永久”饰物了，你应该随身携带一盒，以防万一。

Xiànzài kǒuzhào dōu biàn chéng “bànyǒngjiǔ” shìwù le, nǐ yīnggāi suíshēn xiédài yīhé, yǐ fang wàn yī.

Now masks have become “semi - permanent” items; you should carry a box of them with you, just in case.