Wear One's Heart On One's Sleeve Meaning

Example : 1604, William Shakespeare, Othello, act 1, scene 1, line 64:  Iago: For when my outward action doth demonstrate  The native act and figure of my heart  In compliment extern, 'tis not long after  But I will wear my heart upon my sleeve  For daws to peck at: I am not what I am.1840, Thomas Carlyle, Heroes and Hero Worship, lecture 6:  Such a man must have reticences in him. If he walk wearing his heart upon his sleeve for daws to peck at, his journey will not extend far!1915, Gilbert Parker, The Money Master, ch. 18:  There was something very direct and childlike in Virginie Poucette. She could not pretend; she wore her heart on her sleeve.2011, Calvin Harris, Feel So Close, song:  I feel so close to you right now, it's a force field. I wear my heart on my sleeve, like a big deal.