Origin and history of lamb

Middle English lomb, from Old English lamb, lomb, Northumbrian lemb "lamb, young animal of the sheep kind," from Proto-Germanic *lambaz (source also of Old Norse, Old Saxon, Old Frisian, Gothic lamb, Middle Dutch, Dutch lam, Middle High German lamp, German Lamm "lamb"). Common to the Germanic languages but with no certain cognates beyond them.

The -b probably has been silent since 13c. The Old English plural was sometimes lambru.

As a symbol of Christ (Lamb of God), typified by the paschal lamb, it is attested from late Old English. Also applied to gentle or innocent persons (especially young Church members) from late Old English; from mid-15c. of persons easy to cheat ("fleece"), especially an inexperienced speculator deceived into making bad investments.

Also sometimes used ironically for cruel or rough characters (such as Kirke's Lambs in Monmouth's rebellion, 1684-86, "an ironical allusion to the device of the Paschal Lamb on their flag" [OED]); Farmer and Henley ("Slang and Its Analogues") say "specifically applied to Nottingham roughs, and hence to bludgeon men at elections." Compare lambaste.

Diminutive form lambie is attested from 1718. Lamb's-wool , also lambs-wool, "the wool of lambs" used commercially, hence delicate wool generally (used in hosiery, etc.) is from mid-14c. as a noun (lambwoll), by 1804 as an adjective.