“The togglier was responsible for arming and dropping the bombs in lieu of a bombardier. As the war progressed, the bombing formations would drop when the lead aircraft dropped, and the need for skilled bombardiers decreased. Dropping bombs involved flipping (or toggling) the switch(es) that result in activating the bomb release mechanisms. This is the origin of the title “togglier”, a combination of toggle and bombardier. The lead aircraft crew would include a skilled “group” bombardier, and many of the other crews would utilize toggliers.”
Source: The 401st Bomb Group (H) Association web page http://401bg.org/forum/yaf_postst947_What-is-a-Togglier.aspx#post4314