A
I’ve heard something similar. The two fingers down represent the two natures of Christ, while the three raised fingers (two fingers and thumb) represent the Trinity.I have noticed this hand posture depicted on many paintings, pictures, holy cards, statues, icons, etc…
After poking around, does this explanation sounds plausible?
"Hands are often shown giving a blessing: the last two fingers touching thumb (two fingers raised) symbolizes the two natures of Christ; ring finger touching thumb (three fingers raised) symbolizes the Trinity.
Hands are also shown with with the forefinger extended straight; the middle finger curved slightly; the thumb and the ring finger crossed; and the little finger curved slightly. This gesture forms the letters “IC XC” (Greek letters for “Jesus Christ”) – the first finger making the I, the curved middle finger forming the C, the crossed ring finger and thumb forming the X, and the pinky finger forming the second C."