Semaphore from Greek sēma (sign) + -phoros (carrying), PIE *bʰer- (to carry). Born for the Chappe optical telegraph (1792), reborn for railway signals (1840s), reborn again for Dijkstra's computing primitive (1965). Three centuries, three technologies. Connects referendum and metaphor through the same PIE 'to carry' root.
A system of signalling using visual indicators — movable arms, flags, or lights; in computing, a synchronisation variable controlling shared resource access.
From French sémaphore, coined in 1801 by combining Greek σῆμα (sêma, "sign, signal, mark") and -φορος (-phoros, "bearing, carrying"), from φέρω (phérō, "to carry, bear"). Σῆμα traces to PIE *dʰyeh₂- ("to notice, see") or possibly *seh₂- ("to mark"), though the exact PIE etymology is debated; the word appears in Homeric Greek as the mark on a warrior's tomb or the signal given before battle. Φέρω derives securely from PIE *bʰer- ("to carry, bear"), one of the best-attested PIE roots, yielding Latin ferre ("to carry"), Sanskrit bhárati ("carries"),