It’s easy to mishear a familiar phrase, especially when the alternative sounds plausible in context. That’s exactly what happens when people confuse thickest thieves and thick as thieves. One is an idiom that’s been around for hundreds of years, while the other is a misunderstanding of the phrase.
In this article, we’ll reveal the correct expression, as well as its definition, origin, and examples of how it can be used in real life.
⚡ Quick summary
The correct expression is thick as thieves, meaning “very close friends or partners who share secrets.” The mistaken version, thickest thieves, is an eggcorn — a term for a commonly misheard phrase that still has a degree of logic to it.
Is it thickest thieves or thick as thieves?
The correct phrase, thick as thieves, dates back to the 1800s. In this context, thick doesn’t mean “broad or dense,” but rather “intimate, inseparable, or on very close terms.” That usage has mostly faded from everyday English, but it lives on in this idiom.
Before “thieves” took over, there were other colorful comparisons. In the 18th century, people said things like “thick as inkle weavers.” Inkle weavers were artisans who made narrow woven tape or ribbon called inkle, used for shoelaces, garters, and ties. Because inkle was woven tightly and the weavers often worked side by side at their looms, the saying “thick as inkle weavers” painted a picture of people bound closely together. Over time, thick as thieves became the version that stuck because it provided a vivid image of criminals huddling together, bound by loyalty in their schemes.
Here are a couple of examples:
- Those two have been thick as thieves since college.
- The twins are thick as thieves, always planning something together.
So where does thickest thieves come from? Most likely from a mishearing or reinterpretation — a phenomenon known as an eggcorn. (Other well-known eggcorns include for all intensive purposes, instead of for all intents and purposes, and pass mustard, instead of pass muster.) To modern ears, thick as thieves probably doesn’t make a lot of sense. Without that historical sense of thick as “close or intimate,” people probably assume the phrase must be thickest thieves, since it sounds more natural and “thickest” is a common superlative.
While thickest thieves comes up frequently in speech and online, it doesn’t have the history or idiomatic standing of thick as thieves. Writers and editors consider it an error.
In short, stick with thick as thieves. It’s the established idiom, it has centuries of usage behind it, and it carries that vivid imagery of trust and secrecy. If you write thickest thieves, you may get a chuckle, but it won’t pass muster in polished prose.
