The verb 'thaw' originates from the Old English 'þawian', meaning "to melt, dissolve, or become liquid." This term is of Germanic origin, related to Dutch 'dooien' and German 'tauen', and can be traced back to the Proto-Indo-European root 'tā-', meaning "to melt." The core concept has remained remarkably consistent from its ancient roots to modern usage, specifically describing the transition of a substance from a frozen to a liquid state under the influence of heat. The addition of the '-ed' suffix follows the standard Germanic pattern for forming the past tense and participle, solidifying its grammatical function while leaving the core semantic meaning intact.

The word 'thawed' is the past tense and past participle form of the verb 'thaw'. The root 'thaw' is considered a simplex unit from Old English. The suffix '-ed' is from Old English '-ode' (for weak verbs of the second class) and functions as a past tense and past participle marker.