speak the same language
Understand one another very well, agree with each other, as in Negotiations went on for days, but finally both sides realized they weren't speaking the same language. This term, alluding to literal understanding of spoken words, dates from the late 1800s.
Words nearby speak the same language
speak one's mind,
speak one's piece,
speak out,
speak out of turn,
speak softly and carry a big stick,
speak the same language,
speak to,
speak too soon,
speak up,
speak volumes,
speakeasy