The word 'tailed' is a straightforward morphological construction from the native English root 'tail'. The Old English noun 'tægl' is of Germanic origin, related to Old Norse 'tagl' (horse's hair), and can be traced back to a Proto-Indo-European root meaning 'hair' or 'something long and thin'. The addition of the '-ed' suffix, a versatile grammatical element from Old English '-ed', '-od', '-ad', creates a participial adjective meaning "provided with a tail" or "having the characteristics of a tail." When used as the past tense of the verb 'to tail', the same '-ed' suffix performs its standard grammatical function, marking completed action. Thus, the modern word directly and transparently combines an ancient core concept with a fundamental grammatical marker.

Structure: tail (appendage) + ed (adjective/past participle suffix) tail: From Old English 'tægl', 'tægel', meaning a tail. Its functional role is the core root denoting the appendage. ed: A suffix of Old English origin, used to form adjectives from nouns (meaning "having") and to form the past tense and past participle of verbs.