go way back

go way back (third-person singular simple present goes way back, present participle going way back, simple past went way back, past participle gone way back)

1. (informal) To have been in a (friendly, romantic, etc.) relationship that dates back far into the past.

   He and I go way back.

• “go way back”, in Merriam-Webster Online Dictionary, Springfield, Mass.: Merriam-Webster, 1996–present.