The verb 'tow' originates from the Old English word 'togian', meaning 'to drag, pull', which is related to the Old Norse 'toga'. These Germanic terms likely derive from the Proto-Indo-European root deuk-, meaning 'to lead'. This ancient sense of leading or pulling is directly preserved in the modern meaning. The specific application to pulling vehicles or vessels developed naturally from this core concept. The form 'towed' simply adds the regular past-tense '-ed' suffix to this unchanged root, following standard English conjugation patterns.

The word 'towed' is the inflected past tense and past participle form of the verb 'tow'. It is not productively segmented into separate morphemes in modern English, as the '-ed' suffix is a grammatical inflection, not a lexical morpheme. The core 'tow' is a simplex word.