質問: `どうってことありません。` I know it means `It was nothing.` But, what is `どうって`?
回答: * どうってことない * どうってことありません * どうと言うこともない * etc. are all variations of a set phrase meaning "it's nothing" "it's no big deal". Here どう is just the usual question word and って or と the usual quoting particle. Literally the phrase means that it is not something you would ask/enquire about by saying どう.