fast-flowing

The compound adjective 'fast-flowing' is a transparent modern English formation, combining two native Germanic elements. The first element, 'fast', has an intriguing semantic journey from its Old English meaning of "firm, secure" to its modern sense of "rapid", a shift that occurred in the 13th century, likely influenced by the concept of "securely in one place" evolving into "steadfastly" and then "vigorously". The second element, 'flow', descends from the Proto-Germanic flōaną, related to the act of moving fluidly. The '-ing' suffix, used to form participial adjectives, completes the word, creating a literal and logical descriptor for a river or current that moves with rapid, steady force. The entire construction vividly depicts the characteristic of a stream whose water moves swiftly and continuously.

Structure: fast (quick) + flow (move steadily) + ing (adjective suffix) - fast: From Old English fæst meaning "firmly fixed, steadfast, constant". In this compound, it functions as an intensifying adverb meaning "quickly, rapidly". - flow: From Old English flowan meaning "to flow, stream, issue". It functions as the verbal core of the compound. - ing: A suffix from Old English -ende, -inge, used to form present participles and adjectives from verbs, indicating the action or state of the verb.