Latin name meaning ‘happy, fortunate’, which has from time to time been popular as a given name in Britain and elsewhere because of its auspicious omen. It was in use as a byname in Latin, applied for example to the dictator Sulla (138–178 bc). It was very popular among the early Christians, being borne by a large number of early saints.
Polish: topographic name for someone who lived by a flood plain or a bay, Polish zalew, or a habitational name for someone from a place named with this word, in particular Zalew in Sieradz voivodeship or Zalewo in Olsztyn voivodeship. There has been considerable confusion with Zaleski.