Little Jack Hor ‧ ner /ˌlɪtl dʒæk ˈhɔːnəʳ $ -ˈhɔːr-/ BrE AmE
a character from a ↑ nursery rhyme (=an old song or poem for young children) Little Jack Horner sat in a corner, /Eating his Christmas pie; /He put in his thumb, and pulled out a plum, /And said ‘What a good boy am I’.