The word “eikev“ literally means “heel“. Rashi says that this pasuk is speaking about “minor mitzvos which people trample with their heel.“
The Bais Aharon of Karlin zy”a said, “My children, be very careful with minor aveiros. It is easier to avoid major sins than minor ones. The main focus should be on small sins.”
During the terrifying war years, the Satmar Rov zy”a wrote (in a letter to Rav Yoel Ashkenazi of Teveriah zt”l, printed in Aspaklaria Ha’meirah, Chelek 2, page 102) that the word “eikev“ means “the end“, and the word “tishmi’un“ means “to understand.“ He said: “At this time, we can’t understand why we are facing ‘these laws’, i.e., the terrible decrees facing Klal Yisroel. In the end, however, once the ‘eikev’ arrives, we will understand (‘tishme’un’) everything that Hashem did.“