"one who works for hire," Old English hyrling; see hire (v.) + -ling. Now only disparaging, "one who acts only for mercenary motives," a sense that emerged late 16c. As an adjective by 1580s.
Entries linking to hireling
hire v.
Old English hyrian "pay for service, employ for wages, engage," from Proto-Germanic *hurjan (source also of Danish hyre, Old Frisian hera, Dutch huren, German heuern "to hire, rent"), of uncertain origin. Reflexively, "to agree to work for wages" from mid-13c. Related: Hired; hiring.
-ling
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.