肯定 背后
ken3ding4 bei1hou4
certainly behind
背 肯
bei1 and ken3 look alike but are really different both as ideas and in their sounds. the 月 in both indicates one’s body, flesh. bear it on your back is bei1 the phonetic clue in 背 is bi３比
There is no phonetic clue in ken3 肯 is a combined idea: the STOPPED 止 person and their BODY 月 what is BEHIND the Body of a Stopped person?
I haven’t looked up the etymology of these but even without it we now have good ways to distinguish them.