This is the 17267th most frequent Russian word.
сундуки
"Сундуки" means "chests" or "trunks" in English.
The word 'сундуков' denotes 'chests' in the sense of storage containers, used here in the genitive plural case to align with 'несколько' indicating quantity.
В комнате стояло несколько больших деревянных сундуков.
There were several large wooden chests in the room.
Here, 'сундуки' refers to the chests as objects involved in an action (being opened) and is in the nominative plural form, subject of the sentence.
Искатели приключений открыли древние сундуки, находящиеся в пещере.
The adventurers opened ancient chests located in the cave.
In this sentence, 'сундуки' acts as the direct object (what she cleaned) and is in the accusative plural case, showing the chests are the recipients of the action.