thick as thieves

== English == === Alternative forms === thick as two thieves, close as thieves === Etymology === From thick (“friendly, intimate”), first attested in 1827 as "thick as two thieves". === Pronunciation === === Adjective === thick as thieves (not comparable) (idiomatic, simile, of friends or members of a group) Intimate, close-knit, tight. ==== Usage notes ==== Sometimes used with a connotation that the relationship has a suspicious and/or less than respectable quality. ==== Translations ==== === References ===