"a thing done, a feat or action, good or bad," early 13c., verbal noun from do (v.). From early 14c. as "performance or execution of something." In the former sense, now usually in plural, doings. From c. 1600-1800 it also was a euphemism for "copulation."
dog-tired
dog-tooth
dog-trot
dogwood
doily
doing
do-it-yourself
dojo
dol
Dolby
dolce far niente