Turn the one with the less correct name into a redirect. If there is any chance someone will be searching by the alternative name, might as well let them find it. Also reduces the chances for someone adding that wiki again as another duplicate.
Place #REDIRECT [[Correct Wiki Name]] at the top of the edit box of the 'Incorrect Wiki Name' page (and delete its' contents and ask a sysop to merge their edit histories).
Check source page for useful contents and move it to the 'Correct Wiki Name' destination page.
And leave a note on the talk page of the 'Correct Wiki Name' article indicating the redirect, to help maintain any edit history (and therefore attribution) from the 'Incorrect Wiki Name'.