Idioms often hide a literal past. 'Break the ice' (ease first-meeting tension) originally referred to what?

"Break the ice" traces back to ships literally breaking through ice on frozen waterways to clear a passage for other vessels to follow, a laborious but necessary act of opening up a path. The idiom later shifted metaphorically to describe easing the initial tension or awkwardness when people meet for the first time.

An "ice business" and a "refrigerator" have nothing to do with the phrase's actual maritime origin, even though both superficially relate to ice, showing how idioms can mislead learners who guess based on the literal words rather than the history behind them.

Many social idioms have similarly concrete origins — "clear the air" also comes from a literal, physical sense before becoming a metaphor for resolving tension between people.