'Covert' is Latin for 'thoroughly covered' — the etymological opposite of 'overt.'
Not openly acknowledged or displayed; concealed, secret, disguised.
From Old French 'covert' (hidden, concealed), past participle of 'covrir' (to cover), from Latin 'cooperīre' (to cover completely, to overwhelm), from 'co-' (intensive prefix) + 'operīre' (to shut, to cover, to close). The Latin verb 'operīre' may derive from PIE *wer- (to cover, to shut). 'Covert' is thus etymologically 'thoroughly covered' — hidden from view. It is the doublet of 'covered,' both words descending from the same Old French verb through different paths. Key roots: cooperīre (Latin: "to cover completely"), operīre (Latin: "to shut, to cover, to
Covert and overt are exact opposites built from the same root. 'Overt' comes from Old French 'overt' (open), past participle of 'ovrir' (to open), from Latin 'aperīre.' 'Covert' comes from 'covrir' (to cover), from Latin 'cooperīre.' And 'curfew' is a hidden relative — from Old French 'covrefeu' (cover fire), the evening signal to bank your hearth fire and go indoors.