This is the 391st most frequent Czech word.
musela
"Musela" means "had to" or "must have" (feminine past tense).
Here, 'musela' indicates a conditional form implying that the necessity is hypothetical or dependent on certain conditions.
Musela by být opatrnější.
She would have to be more careful.
This usage of 'musela' shows a requirement or obligation in the past connected to studying for a difficult exam.
Musela se učit na zkoušku, protože byla těžká.
She had to study for the exam because it was difficult.
In this sentence, 'musela' expresses a past necessity or obligation for the speaker (a female identifying individual) to go to the store.