Yes, Yes…   And No, No…
 
In ancient times, people did not want to promise something and say, “I swear by God that I will do this.”  Because they felt that if they swore by God, that they were under obligation to keep their oath, and they often wanted to back out of a promise.  So, people used to say things like…
“I swear by heaven”
“I swear by God’s throne”
“I swear by the earth”
“I swear by Jerusalem”
“I swear by my head that I promise to do this or that”