1860, "to remain clinging," 1860, especially "cling fondly to" (1871); see hang (v.) + on (adv.). As a command to be patient, wait a minute, from 1936, originally in telephone conversations.

verbal phrase; see set (v.) + off (adv.). From 1590s as "make prominent by contrast," 1610s as "adorn." Intransitive sense of "start on or as on a journey" is from 1774. Meaning "separate from contect" (in typography) is from 1824; sense of "ignite, discharge, cause to explode" is from 1810.

1840, from head (n.) + on.

"penile erection," 1922, earlier as an adjective (1893), from hard + on.

"additional component," 1941, from verbal phrase add on; see add (v.) + on (adv.).

"something set aside," especially "commodities, agricultural products, etc., reserved by a government for some special purpose, originally military, 1943, from verbal phrase, probably in the sense of "separate out for a particular purpose" (1720); it originally meant "lay aside temporarily" (late 14c.); see set (v.) + aside (adv.). The verbal phrase also is attested as "dismiss from one's mind, leave out of the question" (c. 1400); "put on one side" (early 15c.); "discard or reject from use or service" (1570s).

"set far downward or inward," originally of eyes, late 14c., from deep (adv.) + set (adj.).

verbal phrase, mid-13c. (intrans.), "express openly, present to view or consideration, make fully known;" c. 1400 as "leave, begin a journey" (set out in the same sense is from late 14c.); see set (v.) + forth (adv.). The notion of set involved in it is "proceed in a specified direction," hence begin to move" (attested from late Old English). From late 14c. as "prepare and send out, issue" (a commandment, etc.). Of a price from 1520s. Intransitive sense of "go, advance, begin to march" is from mid-14c.

"minor non-speaking role," 1902, theatrical slang, from the verbal phrase walk on, attested in theater jargon by 1897 with a sense "appear in crowd scenes," from walk (v.) + on (adv.). Meaning "actor who has such a part" is attested from 1946. The sports team sense is recorded from 1974.

also onsite, 1959, from on + site. Originally in reference to Cold War military inspections.