Why is the ninth month called September?
1550s, "one who chops," agent noun from chop (v.1). Meaning "meat cleaver" is by 1818. Meaning "helicopter" is from 1951, Korean War military slang (cf. egg-beater); as a type of stripped-down motorcycle (originally prefered by Hell's Angels) from 1965.
any of several types of transistors having four semiconducting layers and therefore three p-n junctions; the thyristor is a solid-state analogue of the thyratron vacuum tube, and its name derives from the combination of the two words thyratron and transistor. A common form of thyristor is the silicon-controlled rectifier (SCR), used to convert alternating current (AC) to direct current (DC) and widely used as a component of devices that control motor speeds, liquid levels, temperatures, and pressures.