# thick as thieves

idiom

Source: https://englishreference.com/idiom/thick-as-thieves
Updated: 2026-08-10

## Meaning

Intimate, close-knit, tight.

## Examples

- The two new coworkers are as thick as thieves.
- The two neighbors are thick as thieves and share every secret.
- Ever since they started working on the project together, those two have been as thick as thieves.
- My cousins are thick as thieves and always whisper together in the corner during our large family holiday dinners.
- After spending the whole summer at camp together, the boys returned home thick as thieves and refused to spend a day apart.
- Despite their vastly different backgrounds, the two conspirators became as thick as thieves while planning their daring escape from the city.

## Origin

First attested in 1827 as the longer variant "thick as two thieves," the idiom derives from a specific sense of the word thick denoting a state of close, private intimacy. It implies a degree of friendship so concentrated that the parties involved might reasonably be suspected of conspiring in a shared criminal enterprise. The 1827 citation marks the transition of this particular use of thick from a description of proximity into a fixed social comparison.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.