late 13c., "make deliberate physical contact with," from Old French tochier "to touch, hit, knock; mention, deal with" (11c., Modern French toucher), from Vulgar Latin *toccare "to knock, strike" as a bell (source also of Spanish tocar, Italian toccare), perhaps of imitative origin. Related: Touched; touching.
From c. 1300 in the transitive sense "bring into physical contact," also "pertain to." Other senses attested from 14c. are "perceive by physical contact, examine by sense of touch," also "be or come into physical contact with; come to rest on; border on, be contiguous with;" also "use the sense of touch," and "mention, describe." From early 14c. as "affect or move mentally or emotionally," with notion of to "touch" the heart or mind. Also from early 14c. as "have sexual contact with." Meaning "to get or borrow money" first recorded 1760.
Touch-and-go (adj.) is recorded from 1812, apparently from the name of a tag-like game, first recorded 1650s (however, despite the coincidence, this in no way suggests an acronym origin for tag). Touch football is first attested 1933. Touch-me-not (1590s) translates Latin noli-me-tangere.
c. 1300, from Old French toche "touch, a touching; a blow, attack; a test" (Modern French touche), from tocher "to touch" (see touch (v.)). Meaning "slight attack" (of an illness, etc.) is recorded from 1660s. Sense of "communication" (to be in or out of touch) is from 1884. Sense of "skill or aptitude in some topic" is first recorded 1927, probably from music or the arts. Soft touch "person easily manipulated" is recorded from 1940.
"in a position above and in contact with; in such a position as to be supported by;" also noting the goal to which some action is or has been directed; "about, concerning, regarding; in a position to cover;" as an adverb, "in or into a position in contact with and supported by the top or upper part of something; in or into place; in place for use or action; into movement or action; in operation," Old English on, unstressed variant of an "in, on, into," from Proto-Germanic *ana "on" (source also of Dutch aan, German an, Gothic ana "on, upon"), from PIE root *an- (1) "on" (source also of Avestan ana "on," Greek ana "on, upon," Latin an-, Old Church Slavonic na, Lithuanian nuo "down from").
Also used in Old English in many places where we now would use in. From 16c.-18c. (and still in northern England dialect) often reduced to o'. Phrase on to "aware" is from 1877.