This is the 13786th most frequent Spanish word.
secarnos
"Secarnos" means "to dry ourselves."
In this sentence, 'secarnos' refers to the reflexive action of drying oneself using 'nos' for 'us'.
Debemos secarnos después de nadar.
We must dry ourselves after swimming.
Here, 'secarnos' is used to express the purpose of using the towels, indicating the act of drying ourselves.
Ellos nos prestaron toallas para secarnos.
They lent us towels to dry ourselves.
In this case, 'secarnos' denotes the reflexive action that encompasses 'all of us' as the direct recipients of the drying process.