"intermittently, occasionally," 1530s; see off (adv.) + on. As an adjective, "occasional," from 1580s.

1580s, "advance, proceed," from go (v.) + on (adv.). Meaning "behave, carry on" is from 1777; especially "to talk volubly" (1863). As an expression of derision by 1886.

1909, "with one side facing," from side (n.) + on (adv.), perhaps based on earlier head-on. In reference to a vehicle collision, by 1828.

"concerning, regarding," late 14c., from touch (v.), on model of French touchant.

"gentle rubbing with the palm of the hand," 1886, from French effleurage, from effleurer "to graze, touch lightly, touch upon, strip the leaves off," from ef- "out" (see ex-) + fleur as in the phrase à fleur de "on a level with," from German Flur "a plain, field, meadow" (see floor (n.)).

"excessive sensitivity to touch," 1837, from German hyperaphia (1820s), from Greek aphe "touch;" also see hyper-. Related: hyperaphic "having morbid sensitiveness to touch" (1888).

1900, from thigmo-, combining form meaning "touch," from Greek thigma "touch" + tropism.

1650s, "sense of touch or feeling" (with an isolated instance, tacþe from c. 1200), from Latin tactus "a touch, handling, sense of touch," from root of tangere "to touch," from PIE root *tag- "to touch, handle." Meaning "sense of discernment in action or conduct, diplomacy, fine intuitive mental perception" first recorded 1804, from development in French cognate tact. The Latin figurative sense was "influence, effect."

1610s, "perceptible to touch," from French tactile (16c.) and directly from Latin tactilis "tangible, that may be touched," from tactus, past participle of tangere "to touch," from PIE root *tag- "to touch, handle." Meaning "of or pertaining to the sense of touch" is attested from 1650s. Related: Tactility.

c. 1300, "impose a tax on," from Old French taxer "impose a tax" (13c.) and directly from Latin taxare "evaluate, estimate, assess, handle," also "censure, charge," probably a frequentative form of tangere "to touch," from PIE root *tag- "to touch, handle." Sense of "to burden, put a strain on" first recorded early 14c.; that of "censure, reprove" is from 1560s. Its use in Luke ii for Greek apographein "to enter on a list, enroll" is due to Tyndale. Related: Taxed; taxing.