oscurecer
/oskuɾeˈθeɾ/ · B2 · verb
to darken
🌑 o-SCURE-cer: contains 'obscure' (from Latin obscurus) = to make dark
Oscurecer shares its root with English obscure: both come from Latin obscurus, meaning dark or covered. Spot 'scure' inside it and link it to obscure, then the -ecer ending marks becoming, so it means to grow dark or to darken.