Here's the relevant passage:
> “I know your works: you are neither cold nor hot. Would that you were cold or hot! So, because you are lukewarm, and neither cold nor hot, I am about to spit you out of my mouth.”
This verse uses lukewarm water as a metaphor for indifference or lack of commitment. It is implied that being cold (opposed to God) or hot (committed to God) is preferable to being lukewarm (neither committed nor opposed).
The term "lukewarm" has since become a widely used idiom, often used to describe someone or something that is uninspired, unenthusiastic, or lacking in conviction.
Therefore, the origin of the term "lukewarm" can be traced back to the Bible, where it was used in a metaphorical context to describe spiritual apathy.