[1] : Easton's 1897 Bible Dictionary

sihon
   striking down. the whole country on the east of jordan, from the
   arnon to the jabbok, was possessed by the amorites, whose king,
   sihon, refused to permit the israelites to pass through his
   territory, and put his army in array against them. the
   israelites went forth against him to battle, and gained a
   complete victory. the amorites were defeated; sihon, his sons,
   and all his people were smitten with the sword, his walled towns
   were captured, and the entire country of the amorites was taken
   possession of by the israelites num. 21:21-30; deut. 2:24-37.
   
     the country from the jabbok to hermon was at this time ruled
   by og, the last of the rephaim. he also tried to prevent the
   progress of the israelites, but was utterly routed, and all his
   cities and territory fell into the hands of the israelites
   comp. num. 21:33-35; deut. 3:1-14; ps. 135: 10-12; 136:17-22.
   
     these two victories gave the israelites possession of the
   country on the east of jordan, from the arnon to the foot of
   hermon. the kingdom of sihon embraced about 1,500 square miles,
   while that of og was more than 3,000 square miles.
   

[2] : Hitchcock's Bible Names Dictionary (late 1800's)

sihon, rooting out; conclusion

Sihon >> S Words
Sihon, definition of term: Sihon
sihon_pag1.html