It is important to note that
modern scholarship has
interpreted the
tetragrammaton as
YHWH, which may be a word related to "He who causes to be" (per the
NRSV). The
pronunciation of this as "Jehovah" has no
linguistic basis and is in fact of
late medieval origin.
As far as any mystical value of the number four is concerned, I would point out that the nominative plural of deus is di, a form which was probably just as commonly used in Latin. The Greek "logos," used to identify the divine creative principle, was probably of similar theological importance as theos, but has five letters in the Greek.