odchudzać (Polish) comes from Polish odchudzić, from Polish Chudy, from Old Polish chudy, from Proto-Slavic xudъ, from Proto-Indo-European ksowdós, from Proto-Indo-European k⁽ʷ⁾sewd-, from Proto-Indo-European kes- — to scrape, comb.
odchudzać (Polish): to cause to lose weight, to slim down