The word 'yeller' is a straightforward agent noun formation from the verb 'yell'. The core verb 'yell' originates from the Old English giellan, meaning to shout or make a loud, sharp cry, which itself has Proto-Germanic roots. The addition of the agent suffix '-er', a highly productive morpheme in English, directly creates a noun meaning 'one who yells'. This logical construction follows a common Germanic pattern for forming occupational or descriptive nouns from verbs, such as 'speaker' or 'writer'. The modern term retains the direct link to its root, describing someone who shouts, whether in anger, excitement, or encouragement.

Structure: yell (to shout) + er (person who does) - yell: From Old English giellan, gellan (to yell, to sound harshly), of Germanic origin. It functions as the core verb root. - er: A Germanic agent noun suffix (from Old English -ere), used to form nouns denoting a person who performs the action of the verb.