There will soon appear a translation of Heidegger’s first lecture on thinking. As a preparation, let us look at the relevant German words.
The root is *denk* denken, to think ich denke, I think ich dachte, I thought ich habe gedacht, I have thought bedenken, to think over, deliberate on nachdenken, to ponder
das Denken, thinking der Gedanke, the thought das Gedächtnis, memory das Andenken, rememberance die Andacht, devotion, prayers
bedenklich, doubtful (deserving or worthy of reflection) bedenklicher, (comparative) more doubtful das Bedenklichste, (superlative) the most doubtful (that which is most deserving of reflection)