The expression “to break the ice” means: To dispel coolness or aloofness; to break through reserve or formality, establish friendly relations; also, to start an enterprise.
Literally, of course, it is the ice on a river or lake that is broken for the passage of boats in early spring.
Because that denoted the start of the season’s activity, it was but natural to connect the expression with the start of an enterprise, and it was thus used almost four centuries ago.
The current significance, that of establishing friendly relations, of dispelling reserve, came into general usage through Lord Byron.
In Don Juan (1823) Canto XIII, referring to the British people, he has the noble don say:
And your cold people are beyond all price,
When once you’ve broken their confounded ice.
