This is the 2369th most frequent Polish word.
zaczęło
"Zaczęło" means "started" or "began" in English.
The word 'zaczęło' in this sentence means 'started' and is used as a past tense verb to indicate the initiation of an action (raining).
Zaczęło padać, gdy wychodziliśmy z domu.
It started raining as we were leaving the house.
Here, 'zaczęło' means 'started,' referring to a progressive development or a beginning of enjoyment of an activity (painting).
Pewnego dnia zaczęło mi się podobać malowanie.
One day, I started enjoying painting.
In this usage, 'zaczęło' corresponds to the onset of a change in condition or state (getting dark).