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"instinctive knowledge of the right course of action in any circumstance," 1815, from French, literally "to know (how) to do," from savoir "to know" (from Latin sapere; see sapient) + faire (from Latin facere; see factitious). French also has savoir-vivre "ability in good society; knowledge of customs in the world."
Ease and dexterity in social and practical affairs: “Peter is a friendly person, but he lacks the savoir faire required for a successful career in the foreign service.” From French, meaning “to know how to act.”