gyro (n.)

1560s, "a circular motion," from Latin gyrus "circle, circular course, round, ring," from Greek gyros "a circle, ring," related to gyrós "rounded," perhaps from PIE root *geu- "to bend, curve" (source also of Armenian kor "crooked," Lithuanian gurnas "hip, ankle, bone," Norwegian kaure "a curly lock of hair"). The noun is attested in Middle English only in reference to ship's tackle (early 15c.).

1955, the New York City term for a sandwich elsewhere called submarine, grinder, poor boy (New Orleans), or hoagie (Philadelphia); origin unknown, perhaps so called for its great size (from hero (n.1)), or a folk-etymology alteration of Greek gyro as a type of sandwich.