the youngest child of a family; a weak, puny child;
the smallest and weakest of a brood or litter ...1616 obs. exc. Eng. dial.
from 'nestle-cock' with obscure second element
FIRST DOCUMENTED USE
1616 - see Example below
"...But I, that am his eldest and first borne,
shall have the nesteltrett sett mee beforne"
From: John Lane's Continuation of Chaucer's 'Squire's Tale', 1616
• A New English Dictionary on Historical Principles,
James Murray, 1887-1933
• The English Dialect Dictionary,
Joseph Wright, 1898-1905
• The West Somerset Word-Book,
Frederick Thomas Elworthy, 1886