bi xīn 笔芯

Bi xīn 笔芯 in Mandarine, is the meaning of the refill of pen.

Because the word "refill" has the same pronunciation with "make the gesture of heart", so the "refill"(笔芯) evolve the meaning of "show your like".

The popularity of "bi xīn" (笔芯) was first known by Korean stars. They often uses the shape of the thumb and forefinger to form the shape of the heart to express the love for fans or friends. Gradually, the action of finger to heart has been accepted by more and more stars, and it has been spreading in the fans circle. Later, some netizens felt that the homophonic form sounds ore lovely, and this wording began to become popular.