そっと (sotto) means “gently” | MotiTan Japanese Dictionary

More examples

赤ちゃんが眠っているので、ドアをそっと開けます。aka cha n ga nemu tte i ru no de do a o so tto a ke ma su

Since the baby is sleeping, I gently open the door.

Describes an action done with little force or noise so that it remains unobtrusive.

静かにshizukani: With little or no sound during an action.
ひっそりhissori: In a quiet and unobtrusive way, often without being noticed.

音や動きを目立たせないよう、力を加えすぎず静かに物事を行うさま。oto ya ugo ki o me da ta se na i yō chikara o kuwa e su gi zu shizu ka ni mono goto o okona u sa ma

そっと (sotto) is a native Japanese mimetic adverb, and its internal formation has no established separate source.

English speakers may expect one exact choice between gently and quietly, but this adverb often covers both when an action uses little force and makes little noise.