Secretly means without letting anyone know. Secretly married, secretly pleased, work secretly.
It covers both hidden actions and hidden feelings, and the second is the more interesting: secretly pleased, secretly relieved, secretly hoping — the point being that the feeling contradicts what is shown. Secretly filmed and secretly recorded belong to journalism and to court cases. Note in secret, which is the phrase form; and secretive, which describes the habit rather than a single act.
1adverbsecretlyWithout letting anyone know.
“He secretly planned a surprise party for his wife's birthday.”
2adverbshowingWhile showing the opposite feeling.
“She said she was sorry he was leaving, but she was secretly glad.”
secretly is a manner of concealment.
Also accepted in games: in secret
Proto-Indo-European
*krey-
Latin
sēcrētum
Middle English
secret
English
secret
English, today
secretly
From secret + -ly. secret The noun is from Middle English secret, from Latin sēcrētum. a doublet of secretum. dēagolnes. The verb is from the noun.
Etymology from Wiktionary, CC BY-SA