Mlawa > Mlawka is the name of a river, secondarily transferred to a village and town in northern Poland. The form of the name has not changed since the beginning of its written history. Polish linguists have attempted to connect it with various Slavic words, such as Ukrainian dialectal mlavyj 'weak', or Serbo-Croatian (Bosnian) mlava 'slowly flowing (or weak) stream'. It is demonstrated in the present paper that these words must be separated genetically from the name, because each of them has a different origin. In Slovenian and Serbo-Croatian there is another word family sometimes traced back to an earlier *ml(j)av-. Closer scrutiny reveals, however, that these words must come from *malv(i)- < IE *molHw(eye-) 'to grind, etc.' and consequently have nothing to do with Mlawa.Thus the name Mlawa remains unmotivated within Late Common Slavic and is therefore etymologically unclear, although certain facts may suggest Old Germanic (Gothic?) as its source.