He looked 'familiar' [=he looked like someone I had seen before] but I couldn't remember his name.
Locals refer to the Maple Leaf restaurant 'familiarly' [='informally'] as ‘The Leaf.’
We are 'familiar with' the situation. [=we know about the situation]
(..) precepts in thy memory see thou character Give thy thoughts no tongue, nor any unproportioned thought his act Be thou familiar, but by no means vulgar The friends thou hast and their allegiance tried, grapple them unto thy soul with hoops of steel But do not dull thy palm with entertainment (..)2015 Hamlet