Part of Ramban's comment on Breishit 32:21 offers some insight to this. He says that when Ya'akov sent messengers with a huge gift for Esav, the verse explains part of Ya'akovs thinking where he uses the term "kaparah" - a bit of an unusual term, here. Ramba"n explains that he sent servants before him and gave "kofer nafsho" (loose translation - redemption of his life) by giving this gift, in the similar manner that servants offer kapparah to the king so that they can obtain permission to see the king.
In summary (my analysis), which somewhat concurs with Ramba"n - it is clear that Ya'akov was terrified of Esav - to the point where he thought Esav would kill him. He also understood that Esav had a bit of an ego, and was probably still sore that Ya'kov had cheated him out of the blessing. So to appease Esav's anger, part of Ya'akov's strategy was to consider himself a "servant" to Esav and therefore, by relation, Esav was the "master" or the "Lord". It's a sense of respect, and if nothing else, makes Esav realize that even Ya'akov (at least temporarily) considers Esav the superior "ruler".