The Egyptians were in the habit of taking great oaths. They, piously or not, expressed their impulses by making a solemn appeal to one of their many gods. Through intimate association with them this custom grew to be a habit among the Children of Israel, who also swore by Egypt's gods.
It became necessary to impress upon the minds of Moses' people that the name of God (Jehovah or Yahweh) was a sacred thing, not to be used lightly nor uselessly.
There are many who, while speaking, punctuate their conversation with the names of Deity. How revolting is the habit to man's finer nature, and how repulsive it sounds even to the hardened of heart! God will punish them who use His name carelessly or wantonly.