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Be very friendly, as in He is always wanting to buddy up with me, but I don't really like him. [Slang; early 1900s]
American Heritage Idioms
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Phrase(s): buddy up (to someone)
to become overly familiar or friendly with someone. • Don’t try to buddy up to me now. It won’t do any good. • He always tries to buddy up, no matter how coldly you treat him., Phrase(s): buddy up (with someone)
to join with another person to form a pair that will do something together or share something. • I buddied up with Carl, and we helped each other on the hike. • Carl and I buddied up, and we shared a canoe.
McGrawhill's American Idioms And Phrasal Verbs