The word 'yearling' is a transparent compound formed within English from its native Germanic elements. Its first element, 'year', descends from the Proto-Germanic 'jērą', which itself originates from the Proto-Indo-European root 'yeh₁r-', meaning 'year' or 'season'. The suffix '-ling' is also of Germanic origin, used to form nouns denoting a person or thing connected with the base word. The logic of the word is perfectly literal: a 'yearling' is a creature that has completed one 'year' of life, belonging to that specific age category. This straightforward morphological construction has been consistently used in English since the late 15th century to specify the age of livestock, particularly in agricultural and equestrian contexts.

Structure: year (period of time) + ling (one belonging to) - year: From Old English 'gear', meaning a cycle of seasons, a period of twelve months. Functional role: The core semantic root, indicating the age or time period. - ling: From Old English '-ling', a suffix forming nouns meaning 'one belonging to' or 'one having the quality of'. Functional role: A diminutive or attributive suffix, indicating a person or thing associated with the root.