I'm not sure about Lewandowski, can you tell me? it's very common, however I have heard different things from different sources.
There is extremely large group of surnames in Polish language which stem from the word "lewy" (left), from the name Leon, from the Hebrew name Levi, or from the German name Levin. The stankiewicze.com website lists 278 such surnames. Some of them are as simple as Levi, Levin, Lew or Lewa; some end with -SKI, -CKI, -ICZ, such as Lewanowicz, Lewacki, Lewaczyński, Lewaszki, Lewaszkiewicz, etc.
Significantly smaller group of similar surnames, 77 of all, derives from the word "lawenda", English lavender. To this group belongs Lewandowski
, together with Lewandoski, Lewandowicz, Lewandewski, Lewanderski, Lewandrowski, Lewandziewski, Lewandziński, Lewantowicz. Lawenderski, Lawendowski, etc.
The surname Lewandowski is extremely popular in Poland: 43690 males Lewandowski and 47406 females Lewandowska. This is the seventh most common surname in Poland. Lewandowski, the various mutations of this surname, "lawenda" and lavender all stem from "Lewant", Levant, now: Israel, Jordan, Lebanon, Palestine, Syria and partially Egypt and Turkey. In connection with this etymology of this surname those names were quite popular among Polish (and not only) neophytes from that region.