carry on (v.)

early 14c., "to bear or convey, take along or transport," from Anglo-French carier "transport in a vehicle" or Old North French carrier "to cart, carry" (Modern French charrier), from Gallo-Roman *carrizare, from Late Latin carricare, from Latin carrum originally "two-wheeled Celtic war chariot," from Gaulish (Celtic) karros, from PIE *krsos, from root *kers- "to run."

The meaning "take by force, gain by effort" is from 1580s. The sense of "gain victory, bear to a successful conclusion" is from 1610s; specifically in reference to elections from 1848, American English.

The meaning "to conduct, manage" (often with an indefinite it) is from 1580s. The meaning "bear up and support" is from 1560s. The commercial sense of "keep in stock" is from 1848. In reference to mathematical operations from 1798. Of sound, "to be heard at a distance" by 1858.

To carry out "conduct to completion" is from c. 1600. To carry it off "brazen a thing out" is from 1704; carried off as a euphemism for "killed" is from 1670s. To be carried (away) in the figurative sense "transported, having the attention fully absorbed" is from 1560s. Carrying capacity is attested from 1836. Carry-castle (1590s) was an old descriptive term for an elephant.

"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.