on a first-name basis
Quite familiar and friendly, as in Practically all the guests were on a first-name basis. This idiom alludes to the fact that using a person's given name betokens familiarity. [Second half of 1900s]
Words nearby on a first-name basis
omsk,
omuta,
omw,
on,
on a dime,
on a first-name basis,
on a limb,
on a par with,
on a pedestal, put,
on a rampage,
on a roll