perluvinir

Etymology
From 🇰🇲, as in, the friendship is as cherished as a pearl.

Noun

 * 1) people who are close friends with each other and who get along really well
 * 2)  people who get along really well with each other often describing a temporary situation
 * 1)  people who get along really well with each other often describing a temporary situation

Usage notes
This term can not be used in the singular, nor can it be used describe a group knowing someone else ("They are my good friends"), it can only be used to describe a group of people knowing each other ("All of them are good friends").