Old English lamb "lamb," from Proto-Germanic *lambaz (cf. Old Norse, 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 outside them. Old English plural was lomberu. Applied to persons (especially young Church members, gentle souls, etc.) from late Old English. Also sometimes used ironically for cruel or rough characters (e.g. Kirke's Lambs in wars of 1684-86). Lamb's-wool (adj.) is from 1550s.
A dear, sweet person: Mary is such a lamb (1923+)
(1.) Heb. kebes, a male lamb from the first to the third year. Offered daily at the morning and the evening sacrifice (Ex. 29:38-42), on the Sabbath day (Num. 28:9), at the feast of the New Moon (28:11), of Trumpets (29:2), of Tabernacles (13-40), of Pentecost (Lev. 23:18-20), and of the Passover (Ex. 12:5), and on many other occasions (1 Chr. 29:21; 2 Chr. 29:21; Lev. 9:3; 14:10-25). (2.) Heb. taleh, a young sucking lamb (1 Sam. 7:9; Isa. 65:25). In the symbolical language of Scripture the lamb is the type of meekness and innocence (Isa. 11:6; 65:25; Luke 10:3; John 21:15). The lamb was a symbol of Christ (Gen. 4:4; Ex. 12:3; 29:38; Isa. 16:1; 53:7; John 1:36; Rev. 13:8). Christ is called the Lamb of God (John 1:29, 36), as the great sacrifice of which the former sacrifices were only types (Num. 6:12; Lev. 14:12-17; Isa. 53:7; 1 Cor. 5:7).