mid-15c., "infant at the breast," from suck + diminutive suffix -ling. Similar formation in Middle Dutch sogeling, Dutch zuigeling, German Säugling. Meaning "calf or other young mammal" is from 1520s. Meaning "act of breast-feeding" is attested from 1799. Adjectival sense "not yet weaned" is from 1799.[suckling etymology, suckling origin, 英语词源]