Not sure if I can help with Skald specifically since I've never played it, but my angle for my Half-Orc Dirge Bard might fit.
He was a war drummer, beating the rhythm of battle in accordance to the warlord's commands, up the tempo for offense, slow the cadence for steady advance, trying to be one with the flow of combat.
He discovered his powers when the warlord was caught by a volley of Elven arrows, and his clan's frontline started to collapse, giving way to a massacre.
In despair, he searched for something to guide his hands, he wanted to find the marshalling spirit of his warlord to direct the troops back into array.
He let himself become immersed in the din of battle, the clamor of axes and screams, and deep within it, he found a song. He began playing that rhythm, without any direction, and in its depths, he found a surface, not unlike the surface of his drums.
His beats hit that surface, and when it bounced back, it climbed from that mystical abyss into the souls of his allies. A beat here produced courage, another sent shivers down the spines of his enemies.
You can imagine how this goes. Eventually he discovered that on that surface, he could find souls and "bounce" them back into undeath. Neat!
My Skald character, trained in percussion and song, found his abilities while training to be a blacksmith and armorer. With the rhythm of striking the hot metal, and dance of the sparks, and the cadence of his voice keeping the beat. It ignited some hidden magic within his soul and gave it an outlet. Through the manipulation of sound, he found a way to manipulate the world around him. It was through honing that ability that he found he was also able to manipulate the minds of others and encourage the fighting instinct within.
Not exactly Skald, but my Drow Noble Arcane Duelist Bard was a lone wanderer for most of his life on the surface, having fled the underdark due to "ideological differences".
He now has joined a party, and is learning how to channel his innate Drow magic and his own bravery into a means to Inspire Courage in his allies...
Sometimes he swings his spear overhead waving his banner for all to see.
Sometimes he stands between the party and the enemy with his spear braced and screams a glorious battle cry.
He is only level 5 now, so it's not like he has too much to explain how he learned to do "that"... being a Drow Noble explains the magic, him being a b@d@ss explains the rest.