toutyoudaoicibaDictYouDict
tout: [14] The etymological notion underlying tout is of ‘sticking out, projecting’. It goes back ultimately to the prehistoric Germanic base *tūt- ‘project’, whose other descendants include Dutch tuit ‘spout’. It is assumed to have produced an Old English *tūtian, but it does not turn up in the written record until the Middle English period, by which time the notion of ‘poking out’ had moved on to ‘peeking’ or ‘peeping’. It progressed further to ‘spy on’, but the modern ‘look for business’ did not emerge until the 18th century.
espy (v.)youdaoicibaDictYouDict
early 13c., aspy, from Old French espiier "observe, watch closely, spy on; guard, keep in custody" (12c., Modern French épier), from Vulgar Latin *spiare, from a Germanic source (compare Old High German spehon "to spy;" see spy (v.)). For initial e-, see e-. Related: Espied; espial.
spy (v.)youdaoicibaDictYouDict
mid-13c., "to watch stealthily," from Old French espiier "observe, watch closely, spy on, find out," probably from Frankish *spehon or some other Germanic source, from Proto-Germanic *spehon- (cognates: Old High German *spehon "to look out for, scout, spy," German spähen "to spy," Middle Dutch spien), the Germanic survivals of the productive PIE root *spek- "to look, observe" (see scope (n.1)). Old English had spyrian "make a track, go, pursue; ask about, investigate," also a noun spyrigend "investigator, inquirer." Italian spiare, Spanish espiar also are Germanic loan-words. Meaning "to catch sight of" is from c. 1300. Children's game I spy so called by 1946.
tout (v.)youdaoicibaDictYouDict
1700, thieves' cant, "to act as a lookout, spy on," from Middle English tuten "to peep, peer," probably from a variant of Old English totian "to stick out, peep, peer," from Proto-Germanic *tut- "project" (cognates: Dutch tuit "sprout, snout," Middle Dutch tute "nipple, pap," Middle Low German tute "horn, funnel," Old Norse tota "teat, toe of a shoe"). The sense developed to "look out for jobs, votes, customers, etc., to try to get them" (1731), then "praise highly in an attempt to sell" (1920). Related: Touted; touting.