'lambkin' originates from Middle English, specifically the word 'lambekyn,' where 'lamb' meant 'young sheep' and the diminutive suffix '-kin' indicated smallness or endearment.

'lambekyn' transformed into the modern English word 'lambkin' through Middle English.

Initially, it meant 'a small lamb,' but over time it evolved into a term of endearment for a child or loved one.