Kelcey Ayer—singer, guitarist, and keyboardist—totally just forgot the words.
Still, his co-writer, David Bryan (keyboardist of Bon Jovi), had some ideas for why the musical had connected with voters.
1819, from key (n.1) in sense of "mechanism of a musical instrument" + board (n.1). Originally of pianos, organs, etc., extended to other machines 1846. The verb is first recorded 1926 (implied in keyboarding).