yearling n.

Old English gear (West Saxon), ger (Anglian) "year," from Proto-Germanic *jēr "year" (source also of Old Saxon, Old High German jar, Old Norse ar, Danish aar, Old Frisian ger, Dutch jaar, German Jahr, Gothic jer "year"), from PIE *yer-o-, from root *yer- "year, season" (source also of Avestan yare (nominative singular) "year;" Greek hōra "year, season, any part of a year," also "any part of a day, hour;" Old Church Slavonic jaru, Bohemian jaro "spring;" Latin hornus "of this year;" Old Persian dušiyaram "famine," literally "bad year"). Probably originally "that which makes [a complete cycle]," and from verbal root *ei- meaning "to do, make."

diminutive word-forming element, early 14c., from Old English -ling a nominal suffix (not originally diminutive), from Proto-Germanic *-linga-; attested in historical Germanic languages as a simple suffix, but probably representing a fusion of two suffixes: 1. that represented by English -el (1), as in thimble, handle; and 2. -ing, suffix indicating "person or thing of a specific kind or origin;" in masculine nouns also "son of" (as in farthing, atheling, Old English horing "adulterer, fornicator"), from PIE *-(i)ko- (see -ic).

Both these suffixes had occasional diminutive force, but this was only slightly evident in Old English -ling and its equivalents in Germanic languages except Norse, where it commonly was used as a diminutive suffix, especially in words designating the young of animals (such as gæslingr "gosling"). Thus it is possible that the diminutive use that developed in Middle English is from Old Norse.