Etymology
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nictitate (v.)

"to wink," 1822, from Medieval Latin nictitatus, past participle of nictitare, frequentative of Latin nictare "wink, blink, signal with the eyes," related to nicere "to beckon," from PIE root *kneigwh- "to blink, to draw together (the eyes or eyelids)," source also of Gothic hniewan, Old High German nigan "to bow, be inclined." Related: Nictitated; nictitating (1713). Earlier form was nictate (v.), 1690s, from Latin nictare.

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reveille (n.)

"signal given at break of day to soldiers and sentries" (originally by drum or bugle), 1640s, from French réveillez-vous "awaken!" imperative plural of réveiller "to awaken, to wake up," from re- "again" (see re-) + Middle French eveiller "to rouse," from Vulgar Latin *exvigilare, from Latin ex- "out" (see ex-) + vigilare "be awake, keep watch" (from PIE root *weg- "to be strong, be lively").

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monophonic (adj.)

of recordings, broadcasts, etc., "not stereo, having only one output signal," 1958, coined to be an opposite of stereophonic; from mono- "single" + -phonic, from Greek phōnē "sound, voice," from PIE root *bha- (2) "to speak, tell, say." It was used earlier in music, "pertaining to a style of composition in which one voice-part predominates over the others" (opposed to polyphonic), by 1885.

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taps (n.)
U.S. military signal for lights out in soldiers' quarters (played 15 minutes after tattoo), 1824, from tap (v.), on the notion of drum taps (it originally was played on a drum, later on a bugle). As a soldier's last farewell, played over his grave, it may date to the American Civil War. The tune was revised several times in mid-19c.
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blue peter (n.)

a nautical term for a blue flag having a white square in the center, hoisted at the fore royal masthead as a signal to report on board as the vessel is about to go to sea, attested by c. 1800, from blue (adj.1), but the significance of peter is uncertain and disputed. Two common guesses are that it is an abbreviation of repeater or that it stands for French partir

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microphone (n.)

1680s, "ear trumpet for the hard-of-hearing," coined from Greek mikros "small" (see micro-) + phōnē "sound," from PIE root *bha- (2) "to speak, tell, say." The notion is "instrument for augmenting small sounds." Modern sense of "transducer that converts sound into an electrical signal" is by 1924 in radio broadcasting and movie recording, from the earlier sense "amplifying telephone transmitter" (1878). Of the two spellings of the short form of the word, mike (1924) is older than mic (1961). Related: Microphonic; microphony.

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uxorial (adj.)

"of or pertaining to a wife," 1778, from Latin uxoris (see uxorious) + -al (1). Sometimes is used in the sense of uxorius.

We still say that a husband hangs out the broom when his wife goes from home for a short time; and on such occasions a broom besom has been exhibited as a signal that the house was freed from uxorial restraint, and where the master might be considered as a temporary bachelor. [Samuel Johnson and George Steevens, notes to "The Tempest," 1778]
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advance (n.)
c. 1300, "boasting, ostentation" (now archaic), from advance (v.). Early 15c. as "advancement in rank, wealth, etc.;" physical sense of "state of being in front" is from 1660s; that of "a move forward or toward the front" is from 1670s. Commercial sense of "something given beforehand" is from 1680s (earlier in this sense was advancement, 1640s). Meaning "military signal to advance" is by 1849. Also "an act of approach" (1670s), hence advances "amorous overtures" (1706).
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SOS 
1910, from International Morse code letters, chosen arbitrarily as being easy to transmit and difficult to mistake. Not an initialism (acronym) for "save our ship" or anything else. Won out over alternative suggestion C.Q.D., which is said to mean "come quickly, distress," or "CQ," general call for alerting other ships that a message follows, and "D" for danger. SOS is the telegraphic distress signal only; the oral equivalent is mayday.
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buoy (n.)
"float fixed in a place to indicate the position of objects underwater or to mark a channel," late 13c., boie, probably from Old French buie or Middle Dutch boeye, both of which likely are from Proto-Germanic *baukna- "beacon, signal" (see beacon). OED and Century Dictionary, however, suggest it is from Middle Dutch boeie or Old French boie "fetter, chain" (see boy), "because of its being fettered to a spot."
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