familiar 有名词密友，常客的意思吗？

有的。
webster的解释：
1 : a member of the household of a high official
高官家里的成员；

2 : one that is familiar; especially : an intimate associate : COMPANION
熟悉的人；

3 : a spirit often embodied in an animal and held to attend and serve or guard a person
一种精灵，常常在动物身上附体，用来照顾、服务或保护一个人；

4 a : one who is well acquainted with something b : one who frequents a place
a：对。。。很熟的人；b：常去某个地方的人

有，不过不常见，你看看一下的英文解释：
名词 familiar:
a person attached to the household of a high official (as a pope or bishop) who renders service in return for support
a person who is frequently in the company of another
同义词：companion, comrade, fellow, associate
a spirit (usually in animal form) that acts as an assistant to a witch or wizard
同义词：familiar spirit

familiar

adj.
熟悉的, 常见的, 听惯的, 亲近的, 随便的
n.
密友, 熟客, 常客

进一步解释：
1. Familiar implies an easy, often informal association base