This is just a very rare Old Testament Biblical name. There is a man named Ela mentioned in the book of I Kings, Chapter 4, Verse 18, as one of
King Solomon's twelve officers responsible for supplies.
If the name has been in the family since the 1700s, it is possible that the original Ela was born at a time when some families still sometimes chose names for children by opening the Bible at random, and using the first name they saw on that random page.