Break the ice
A person who breaks the ice is someone who does or says
something to make people relax in an uncomfortable situation.
The earlier meaning of this phrase, i.e. ‘to forge a path for others to follow’ alludes of course to the breaking of ice to allow the navigation of boats. The figurative use is quite old and was recorded by Sir Thomas North in his 1579 translation of Plutarch’s Lives of the noble Grecians and Romanes:
“To be the first to break the Ice of the Enterprize.”
It wasn’t until the latter part of the 17th century that it took on its current ‘establish a relaxed relationship in socially awkward situations’ meaning. For example, Samuel Butler’s Hudibras, 1678:
“The Oratour – At last broke silence, and the Ice.”
Newtons theories broke the ice for modern age physics.