baixest

Probably from baix (“low”) with the ending -est by analogy with forest. Alternatively, from earlier beixest (“leap year”) (from Latin bisextus), by a chain of association: "leap year" > "year of misfortune" > "depression in the landscape", with a change in spelling due to association with baixar (“descend”). In the latter case, a doublet of bixest.

baixest m (plural baixests or baixestos)

1. (archaic) slope, declivity
2. (geography) depression, especially one enclosed by higher terrain; coombe

   Synonym: baixura

• “baixest”, in Gran Diccionari de la Llengua Catalana, Grup Enciclopèdia Catalana, 2024}
• “baixest” in Diccionari normatiu valencià, Acadèmia Valenciana de la Llengua.
• “baixest” in Diccionari català-valencià-balear, Antoni Maria Alcover and Francesc de Borja Moll, 1962.