Origin and history of weakling

c. 1300, weik, "deficient in bodily strength; exhausted from exertion," also "lacking moral strength;" from Old Norse veikr "lacking strength," which is cognate with Old English wac "weak, pliant, soft."

They are reconstructed to be from Proto-Germanic *waika- "yield" (source also of Old Saxon wek, Swedish vek, Middle Dutch weec, Dutch week "weak, soft, tender," Old High German weih "yielding, soft," German weich "soft"), which according to Watkins is from PIE root *weik- (2) "to bend, to wind."

Of tools, etc., "lacking effectiveness," early 14c.; of things, "fragile, breakable," late 14c. Specifically of substances, medicines, "not sufficiently imbued with the usual qualities or ingredients," 1590s.

Of a person, especially an opponent or enemy, "lacking fighting skill, deficient in combat power," early 14c. The sense of "lacking authority over others" is recorded by late 14c.

In grammar, denoting a verb inflected by regular syllabic addition rather than by change of the radical vowel, from 1833, in contrast to strong (adj.).

Of the voice by early 14c. In reference to a pulse, "faint," by 1700. Related: Weakly; weaker; weakest.

Figurative expressions about a chain being no stronger than its weakest link are attested by 1846. Weaker vessel as a figurative phrase for "woman" is by 1520s; in Tyndale's New Testament weak translates Greek asthenōn, which St. Paul used in reference to any believer whose faith was beset by doubts and who should be treated tenderly and patiently. Compare weakling.

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.