Nearly all families that have any of the following spelling variations have been researched by me and I have built family trees of those families: Efron, Effron, Affron, Ephron, Efran, Effront. But that is not everything.
Some families related to the families that used the above spellings use a spelling which is typically used by Irish families: Heffron. In Boston, a large Jewish Heffron family established itself 100 years ago, and they are definitely Efrons -- they just use an unusual spelling.
And some related, Jewish families or small parts of families use other spellings: Efrein, Efrin and Hafron, for example. All families who spell their names in one of these ways has been researched by me.
Those of course are English spellings, and there are many variations of spelling the name in Hebrew as well. First of all, in Hebrew the name starts with an Ayin or an Aleph, two different vowels. The second vowel in the name is usually a Vav, giving the second vowel and "O" sound, but there are variations on that as well.
The Belgium enzymologist Jean Effront used a decidedly French or Swiss spelling, just as the Boston Heffrons found themselves using a decidedly Irish spelling.
The most universal spelling is EFRON, but perhaps the most common English spelling is EFFRON.
The AFFRON families were found primarily in Kingston, NY, from whence they've since spread.
EPHRON is used by certain branches or sub-branches, and is the accepted Engish spelling of the Biblical character from Genesis, who drives a hard bargain with the Patriarch Abraham in order to sell Abraham a burial place for his wife, Sarah.
It is unlikely that the source of the name EFRON (and its variants) is from the biblical Ephron the Hitite, who sold Abraham the Cave at Macphelah. The source of this family name will need wait for another Blog posting.