means To melt from a frozen state, or to warm and soften — whether literally turning ice to water or figuratively easing tension between people.

from From Old English thawian, 'to melt,' tracing back to a Proto-Germanic root (cousin to Dutch dooien and German tauen) and likely further to a Proto-Indo-European base meaning 'to dissolve or melt away.' The figurative thaw — of moods, of relations between nations — is a much later flowering of the same simple image: hard things going soft as the cold lets go.