The word 'yellowed' is a straightforward English formation. Its base, 'yellow', descends from the Proto-Germanic 'gelwaz', which itself can be traced back to the Proto-Indo-European root 'ghel-', meaning 'to shine' and associated with bright colors like yellow and green. The addition of the adjectival suffix '-ed', common in Germanic languages, creates a participial adjective that describes the state of having acquired a yellow color. Thus, the modern term 'yellowed' logically conveys the process or result of something turning yellow, most often due to the passage of time, exposure, or deterioration.

Structure: yellow (color) + ed (adjective suffix) - yellow: From Old English 'geolu', 'geolwe', of Germanic origin, related to Dutch 'geel' and German 'gelb'. Functions as the base adjective denoting the color. - ed: A suffix of Germanic origin used to form adjectives from nouns or other adjectives, indicating possession of a quality.