"confident of performance," by 1952, from expression can do "it is possible" (1903), literally "(I or we) can do (it)," which is perhaps based on earlier no can do (see no).
the city's indomitable optimism and can-do spirit
a can-do kind of person
candle
candle-light
Candlemas
candlestick
candle-waster
can-do
candor
candour
candy
candyass
candy-striper