The Yodh Heh symbol shows up frequently on the internet and on publications, (particularly in conjunction with the Syriac Church) however it is rare to find its explanation or history.
The early Syrian Christians, when composing their texts, relied on earlier Aramaic texts of the Torah (law), Neviim (prophets) and Ketuvim (writings). In these Aramaic texts, the full name of God or the Tetragramaton, was never fully written out, but was abbreviated as Yah out of respect for the name, much as Jews of today refer to Him merely as HaShem (the name) or Adonai (Lord). Fast forward to the birth of the faith, Jesus' name in Aramaic is Yahshuo which means "God saves". For this reason, both He and God in the early Christian texts were referred to as Mar Yah. (Mar = Lord, thus... Lord God) This clearly shows that the early Christians did believe that Christ was, in fact, God. The Peshitta leaves no doubt whatsoever that Jesus was God Himself, manifest in the flesh.
- Examples: Luke2:11 - "For unto you is born this day in the city of David a Saviour, which is Christ the Lord God (Mar Yah)"
- 1 Corinthians 12:3 "and that no man can say that Jesus is the Lord God (Mar Yah) but by the Holy Spirit."
- Matthew 22:43 "He said to them, How is it then that David through the spirit calls him Lord God?"
- Mark 12:29 "Jesus said to him, The first of all commandments is, Hear, O Israel, the Lord our God is one Lord God (Mar Yah)"
- Acts 10:36 For God sent the word to the children of Israel, preaching peace and tranquility by Jesus Christ; he is the Lord God (Mar Yah) of all.
There are literally thousands of such verses in the Aramaic which show both God and Jesus both being referred to as Mar Yah (Lord God). Thus, in the Syriac Church, the Holy Name Yah became a symbol of God and of Christ, and of the oneness of the physical and heavenly manifestations of the one God.
Regardless, this tradition continued on through the Syriac Church as a "Nominum Sacrum" (and sadly impressions of the name were used even as talismans among Muslims). The three dots above the two written letters represent the three parts of the one God, the two letters represent His two wills (The Yod being the higher or Godly will Y'Chshab = thought, and the Heh being the lower or earthly will Ha'aydin = to do) of Christ, and the single dot on the bottom indicates the Ihadaya... the oneness of God. It is not known if the dots were formulated first and vowel markings came to be based upon them, or if the vowel markings came first and conveniently taught sacred theology.