on countless occasions; many a time; time and again
Emphasizes that something has happened repeatedly over a long period or many times, often with a sense of frequency that is hard to count. Used in both spoken and written Japanese.
He has helped me on countless occasions.
This issue has been discussed many a time.
Combination of 幾度 (ikudo, 'how many times') + となく (to naku, 'without being specified'), literally 'without saying how many times'. The expression is a fixed adverbial phrase.