roc

rock

Related: solide comme un roc

From Middle French roc (15th c.), ultimately from Latin rocca, whence also roche. The Trésor informatisé considers it a “masculine form” of the latter, but the derivation is dubious, unless it were from a dialect with preserved /k/ (such as Picard or Occitan).

rook

From Old French roc, ultimately from Persian رخ (rox), from Middle Persian lhw' (rox, “rook, castle (chess)”), possibly from Sanskrit रथ (ratha, “chariot”).