also a.w.o.l., military initialism (acronym) for absent without leave (the phrase itself is attested by 1767 in a military context). In U.S. military use by 1917. According to the "Dictionary of Contemporary American Usage" (1957), it was pronounced as four letters in World War I, as a word in World War II.
also jack-boot, 1680s, type of large, strong over-the-knee cavalry boot of 17c.-18c., later a type worn by German military and para-military units in the Nazi period. From jack (n.), though the exact sense here is unclear + boot (n.1). Figurative of military oppression since 1768. Related: Jackbooted.
cognomen of the mad, extravagant, and legendarily cruel third Roman emperor (12 C.E.-41 C.E.), born Gaius Caesar. The nickname is Latin, literally "little boot," given when he joined his father on military campaigns when still a toddler, in full, child-sized military gear; it is a diminutive of caliga "heavy military shoe," which is of unknown origin.
small electronic device, 1948, from transfer + resistor, so called because it transfers an electrical current across a resistor. Said to have been coined by U.S. electrical engineer John Robinson Pierce (1910-2002) of Bell Telephone Laboratories, Murray Hill, N.J., where the device was invented in 1947. It took over many functions of the vacuum tube. Transistor radio is first recorded 1958.
"to instruct in military exercise," 1620s (a sense also found in Dutch drillen and the Danish and German cognates), probably from drill (v.1) on the notion of troops "turning" in maneuvers. Related: Drilled, drilling.
As a noun, "act of training soldiers in military tactics," 1630s; the extended sense of "the agreed-upon procedure" is by 1940. Drill-sergeant "non-commissioned officer who instructs soldiers in their duties and trains them in military movements" is by 1760. Drill-master "one who gives practical instructions in military tactics" is by 1766.