Here's why this phrase is understood this way:
* Fighting is often associated with being "outside": It's less likely for people to physically fight inside a building or enclosed space.
* "Taking it outside" implies a more serious conflict: The phrase suggests that the conflict has escalated beyond words and that a physical confrontation is necessary.
However, it's important to note that "take it outside" can have different meanings depending on the context. For example, it could mean:
* "Let's have a private conversation": If someone says "take it outside" in a heated discussion, they might be suggesting a more calm and private setting to continue the conversation.
* "Let's go outside for a break": This could be a suggestion to take a break from a stressful situation and enjoy some fresh air.
Ultimately, the meaning of "take it outside" will depend on the context and the tone of the speaker.