The Heart is a Container for Love

Description of motion: Hands start inward near the center of the chest with the palms facing each other.  They move in an "opening" gesture.
Observed:  1-14-2015.  Rad School Meeting.  13 people seated around long table.  Seated.
Example:  "I'm a private person, but over the course of the last few years, I've really started opening up."
Link to use:  How to Open Your Heart
Use:  Used to show a willingness to enter into communion with others, typically in reference to the heart.  Could imply an unshielding, a release from overprotection.  
Metaphor:  The Heart is a Container for Love. 
Explanation:  The bodily feeling of the warmth of love is typically associated with the chest area and more specifically with the heart itself.  The gesture begins at the heart and from there performs a movement of opening.  What is implied here is that the heart is a place that stores love, or at least experiences it.  Because it is the place that experiences love, it is also sensitive, and so there is a healthy amount of defensive shielding that is required when entering the communal world of social interaction.  However, because of this defensive strategy, there develops the tendency to over-shield the heart, thus making it incapable of performing its designated task, to love.  Opening up is a momentary relinquishing of defenses and an embrace of the communal world of human interaction.  It implies a willingness to risk harm for the greater goal of love.
Origin: I would imagine the origin of such an association, heart/love, is because when we have deep communal feelings towards others, it is typically associated with a warmth in that particular part of the body, as well as the pain when love is "taking away".  The heart is sometimes though of as the most important organ in the body, and so it would be natural to associate that feeling with the organ itself, as the experience of love is also often thought of as extremely important.
Note on categorization:  I categorized this under Absorption, because the act of opening up implies a willingness to accept something from the outside into the inside, such as the act of opening a door.  You are first, letting something in, such as a person into your house.   There could also be an argument that "opening up" should be categorized under Bonds, as the end result of this action is to create stronger bonds between you and someone else.  While this is implied in the gesture, it isn't necessarily the result.  Someone could "open up" and only experience further "heartache".