He was probably named after his paternal grandfather, Mieszko I. His second name, Lambert, sometimes erroneously considered to be a nickname, was given to him as a reference to Saint Lambert.
El a fost, probabil, numit după bunicul său din partea tatălui, Mieszko I. Cel de-al doilea nume, Lambert, considerat uneori în mod eronat ca fiind o poreclă, i-a fost dat ca o trimitere la cultul sfântului Lambert.