"one who observes flights of birds for the purpose of taking omens," 1590s, from Latin auspex "interpreter of omens given by birds," from PIE *awi-spek- "observer of birds," from root *awi- "bird" + root *spek- "to observe." Compare Greek oionos "bird of prey," also "bird of omen, omen," and ornis "bird," which also could mean "omen."
"sharp-sighted," also "of acute mental discernment," 1630s, formed as an adjective to perspicacity, from Latin perspicax "sharp-sighted, having the power of seeing through; acute," from perspicere "look through, look closely at," from per "through" (from PIE root *per- (1) "forward," hence "through") + specere "look at" (from PIE root *spek- "to observe"). Related: Perspicaciously; perspicaciousness.
1925, from omphalo- + Greek -skepsis, from skeptesthai "to reflect, look, view" (from PIE root *spek- "to observe"). Also omphaloscopy (1931). Used earlier in the sense of "navel-gazer" were omphalopsychic (1892) and Omphalopsychite (1882) "one of a body of monks who believed the deep contemplation of the navel induced communion with God," a derisive name given to the Hesychasts.
Old English oferseon "to look down upon, keep watch over, survey, observe;" see over- + see (v.). Meaning "to supervise to superintend" is attested from mid-15c. The verb lacks the double sense of similar overlook, but it sometimes had it and this survives in the noun form oversight. Compare German übersehen, Dutch overzien. Related: Oversaw; overseen.
1640s, from Italian telescopio (Galileo, 1611), and Modern Latin telescopium (Kepler, 1613), both from Greek teleskopos "far-seeing," from tele- "far" (from PIE root *kwel- (2) "far" in space or time) + -skopos "watcher" (from PIE root *spek- "to observe"). Said to have been coined by Prince Cesi, founder and head of the Roman Academy of the Lincei (Galileo was a member). Used in English in Latin form from 1619.
c. 1200, noten, "observe, take mental note of, mark carefully," from Old French noter "indicate, designate; take note of, write down," from Latin notare "to mark, note, make a note," from nota "mark, sign, note, character, letter" (see note (n.)). Sense of "mention separately or specially among others" is from late 14c. Meaning "to set down in writing, make a memorandum of" is from early 14c. Related: Noted; noting.
"state or character of being perspicacious; keenness of sight, clearness of understanding," 1540s, from French perspicacité (15c.) and directly from Late Latin perspicacitas "sharp-sightedness, discernment," from Latin perspicax "sharp-sighted, having the power of seeing through," from perspicere "look through, look closely at," from per "through" (from PIE root *per- (1) "forward," hence "through") + specere "look at" (from PIE root *spek- "to observe"). An earlier word was perspicience "ability to see all things, infinite vision" (c. 1400).
"abstain from food," Old English fæstan "to fast" (as a religious duty), also "to make firm; establish, confirm, pledge," from Proto-Germanic *fastanan "to hold, guard," extended to the religious act "observe abstinence" (source also of Old Frisian festia, Old High German fasten, German fasten, Old Norse fasta "abstain from food"), from the same root as fast (adj.).
The original meaning in prehistoric Germanic was "hold firmly," and the sense evolved via "have firm control of oneself," to "hold oneself to observance" (compare Gothic fastan "to keep, observe," also "to fast"). Perhaps the Germanic sense shifted through use of the native words to translate Medieval Latin observare in its sense "to fast," or it might have been a loan-translation of a Greek expression brought to the Goths by Arian missionaries and spread from them to other Germanic peoples. The verb in the sense "to make fast" continued in Middle English, but was superseded by fasten. Related: Fasted; fasting.