Possible meanings are 1) "song people sang while going up to Jerusalem for a celebration" or 2) "song people sang while going up the steps into the temple" or 3) "song whose words are like steps." See how you translated this in [Psalms 120:1](../120/001.md)
Things that are too hard for a person to understand are spoken of as if they are beyond the person or too far away from the person to be able to reach them. AT: "things that are too hard to understand" (See: [[rc://en/ta/man/translate/figs-metaphor]])