usbu al-shahada = finger of shahada (shahada is the first pillar of islam)
The blood in the first image signifies martyrdom
This article explains the sign and its usage in detail (which Snopes tried to debunk)....
https://www.americanthinker.com/blog/2015/02/rebutting_snopes_on_obamas_muslim_gang_sign.html
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Just after Obama walked on stage, an off-camera voice coming from behind him cried, “Allahu Akbar.” This is a Muslim expression meaning “God is the greatest,” a cry that Muhammad, the creator of Islam, made frequent use of to incite people to violence and to praise their violent deeds.
Obama’s hand gesture was in response to this cry. It happened quickly. Eight seconds into the video below (https://www.youtube.com/watch?v=Fc6XHQHeWnM&feature=youtu.be&t=8s), you can see that he raises his right hand rapidly, and as it reaches the level of his face, a thumbs-up gesture has formed. His hand then disappears behind his head for the briefest moment, and when it reappears, his thumb is folded under his index finger.
It is by then a fully formed and perfectly executed usbu al-shahada – the finger of shahada, shahada being the fundamental declaration of faith of Muslims: There is but one God and Muhammad is his messenger. This is not finger-pointing, or making a point, or getting attention in order to ask a question, or the wagging of a finger.
The blood in the first image signifies martyrdom