gyromancy (n.)
1550s, method of divination by walking in a circle till the person falls down from dizziness, the inference being drawn from the place in the circle at which he fell, from Medieval Latin gyromantia, from Greek gyyros "circle" (see gyre) + manteia "divination, oracle" (see -mancy).
gyroscope (n.)
heavy rotating wheel with an axis free to turn in any direction, 1856, invented and named in French 1852 by Foucault, from Greek gyros "circle" (see gyre) + skopos "watcher" (see scope (n.1)), because the device demonstrates that the earth rotates.
gyroscopic (adj.)
1871, from gyroscope + -ic. Related: Gyroscopically.
gyrostat (n.)
1879, from gyro- + -stat.
gyrostatics (n.)
branch of dynamics dealing with rotating bodies, 1883, from gyrostatic (1879); see gyrostat + -ics.
gyrus (n.)
convolution between grooves, 1842, from Latin gyrus "circle, circuit, career," from Greek gyros "ring, circle" (see gyre).