The word 'teething' is a straightforward English formation built upon the ancient Germanic root for 'tooth'. The Old English noun 'tōþ' can be traced back to the Proto-Germanic 'tanþs', which itself derives from the Proto-Indo-European root 'h₃dónts', 'h₃dent-', meaning 'tooth'. The addition of the nominal suffix '-ing', a productive suffix in Old English used to form nouns of action, transforms the static object ('tooth') into the dynamic process ('teething'). Thus, the modern term logically and literally describes the process of teeth emerging through the gums, a meaning directly inherited from its constituent parts.

Structure: tooth (noun) + ing (noun suffix) - tooth: From Old English 'tōþ', of Germanic origin; related to Dutch 'tand' and German 'Zahn'. It functions as the base noun denoting the hard structure in the mouth. - ing: From Old English '-ung', '-ing', a suffix forming nouns from verbs, indicating an action or process.