To develop mold
Mold grew on it. By metaphor: it became stale. It lost its freshness.
(Modern Hebrew)
Translation
Expression (Hebrew)
הֶעֱלָה עֹובֶשׁ
Definition (Hebrew)
צָמַח עָלָיו עֹבֶשׁ. בְּהַשְׁאָלָה: הִתְיַשֵּׁן. אָבַד עָלָיו הַכֶּלַח.
(הָעִבְרִית הַחֲדָשָׁה)