observeyoudaoicibaDictYouDict[observe 词源字典]
observe: [14] Latin observāre meant ‘watch, pay attention to, look to, comply with’. It was a compound verb, formed with the prefix ob- ‘to’ from servāre ‘keep safe’, hence ‘guard, watch, heed’ (no relation to servīre, source of English serve and servant). The two semantic strands ‘seeing, noting’ and ‘complying’ have remained together in the English verb, but have diverged in its derived nouns, the former going to observation [14], the latter to observance [13].
=> conserve, reserve[observe etymology, observe origin, 英语词源]
achtungyoudaoicibaDictYouDict
German word used to command attention, from German achtung, from acht (n.) "attention, care, heed, consideration," achten (v.) "pay attention to, regard, esteem, respect," from Old High German ahton "pay attention to," a general Germanic word akin to Old English eahtian "to estimate, esteem, consider, praise," but with no living native descendants in English.
five (n.)youdaoicibaDictYouDict
Old English fif "five," from Proto-Germanic *fimfe (cognates: Old Frisian fif, Old Saxon fif, Dutch vijf, Old Norse fimm, Old High German funf, Gothic fimf), from PIE *penkwe- (cognates: Sanskrit panca, Greek pente, Latin quinque, Old Church Slavonic peti, Lithuanian penke, Old Welsh pimp). The sound shift that removed the *-m- is a regular development involving Old English, Old Frisian, and Old Saxon (as in thought, from stem of think; couth from *kunthaz; us from *uns).

Five-and-ten (Cent Store) is from 1880, American English, with reference to prices of goods for sale. Five-star (adj.) is from 1913 of hotels, 1945 of generals. Slang five-finger discount "theft" is from 1966. The original five-year plan was 1928 in the U.S.S.R. Five o'clock shadow attested by 1937.
[under picture of a pretty girl] "If I were a man I'd pay attention to that phrase '5 O'Clock Shadow.' It's that messy beard growth which appears prematurely about 5 P.M." [Advertisement for Gem razors and blades, Life," May 9, 1938]
obey (v.)youdaoicibaDictYouDict
late 13c., from Old French obeir "obey, be obedient, do one's duty" (12c.), from Latin obedire, oboedire "obey, be subject, serve; pay attention to, give ear," literally "listen to," from ob "to" (see ob-) + audire "listen, hear" (see audience). Same sense development is in cognate Old English hiersumnian. Related: Obeyed; obeying.
tutor (n.)youdaoicibaDictYouDict
late 14c., "guardian, custodian," from Old French tuteor "guardian, private teacher" (13c., Modern French tuteur), from Latin tutorem (nominative tutor) "guardian, watcher," from tutus, variant past participle of tueri "watch over," of uncertain origin, perhaps from PIE *teue- (1) "pay attention to" (see thews). Specific sense of "senior boy appointed to help a junior in his studies" is recorded from 1680s.