Origin and history of tout

1700, thieves' cant, "act as a lookout, spy on," from now-obsolete tout "peep, peer, look out, gaze" (Middle English tuten, toten), which is probably from a variant of Old English *tutian, totian "to stick out, stand out; peep, peer."

This is reconstructed to be from Proto-Germanic *tut- "to project" (source also of Dutch tuit "sprout; snout," Middle Dutch tute "nipple, pap," Middle Low German tute "horn, funnel," Old Norse tota "teat, toe of a shoe").

The English cant verb later was used especially in racing slang, "spy out horses in training to glean information for betting purposes." The other colloquial sense development is from "act as a lookout" 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. Touter as "one who goes about soliciting custom for an inn, coach line, etc." is by 1754; as "a spy on race horses" by 1812. In Middle English to touten oute was "jut out, project, protrude."

Toute (n.) was "projection of rock and earth, hill;" also "rump, buttocks" (c. 1300, as in the Miller's Tale), probably from the verb tout or a noun in Old English. Later, tout (n.) is attested as thieves' slang for "scout, watchman" by 1718; it is recorded by 1853 in reference to one who solicits custom, and by 1865 in the horse racing sense. 

A toting-hill was an observation place, also tote-hill, which probably is preserved in English place-names.