No, it’s not an elided part of a Nike commercial.
doit (n.) IPA Pronunciation: 
small sum, worthless amount, trifle
TRINCULO
Where they will will not give a doit to relieve a lame beggar…
– The Tempest (II.ii)
A doit was a small Dutch coin that was worth half an English farthing, which wasn’t much. So half of that (and perhaps the fact that it was Dutch) made it a worthless amount.