In poland/polish laguage there are (at least) two known proverbs/sayings about name Maciej.W kółko Macieja.Maciej zimę traci albo ją bogaci.The second one, as far as I know, relates to the name's birthday (24-25 feb). It's meant to be sort of a weather forecast for the end of winter time.
It happens that it is my first name too. I agree that this name is quite unique, especially in the polish version where the letter "j" is used, the only variation of this name with a "j" letter. ;) However, I personally don't like being called this. I prefer Maciek :/
There were two Polish politicians among those who bore this name: Maciej Rataj, pre-war PSL (agrarian party) leader, Speaker of the Parliament, twice Acting President of Poland; murdered by the Nazis; Maciej Plazynski, moderate right-wing MP, Speaker of the Parliament, co-founder of the Civic Platform (the currently ruling party, yet he left the Platform soon after founding); killed in the Smolensk air crash. The name Maciej was long associated with peasants, so a popular cap worn by Polish farmers was called "maciejowka".
The Polish International Maciej Zurwaski played for the Polish team Legia Warsaw I think and now he plays for the Scottish team Celtic where he is known as Magic.
Source: https://forebears.io/poland/forenames