I need a two-word literary, good-sounding (I know, it sounds vague), and ironic phrase to say something like unknown acquaintances. I want two sides of the phrase to contradict each other. We have an ideal phrase for this in my native language and it sounds something like "people whom we know (acquaintances) whom we don't know." This phrase, however, sounds succinctly as "tanımadığımız tanışlar" where "tanı" means to know/recognize. Now, I am searching for an English alternative of that phrase.
So, here is a bit of context: I am talking about speaker series and I want to invite people whom we meet routinely every single day but don't attempt to get to know them. Examples of such people may be gardeners, dining staff, waiters, police, janitors/janitresses etc.