be on first name terms (with somebody)
From Longman Dictionary of Contemporary Englishbe on first name terms (with somebody)be on first name terms (with somebody)British English, be on a first name basis American EnglishKNOW somebody to know someone well enough to call them by their first name → first nameExamples from the Corpusbe on first name terms (with somebody)• Voice over Even the governor is on first name terms with the inmates, although the staff still keep a respectful distance.