Source entered the English language in the mid 1300s to mean ‘support, base’, later that century meaning ‘first cause, origin’. Etymologically, the Source is something that has surged up, a most appropriate word to denote the way that Life bubbles up from the Divine Origin of the Universe, like a sparkling fountain, in the Eternal Now.
From Old French sourse ‘a rising, beginning’, mundanely the ‘fountainhead of a river or stream’, feminine noun use of the past participle of sourdre ‘to rise, spring up’, from Latin surgere ‘to rise, arise, get up, stand up’, from sub ‘up from below’, from PIE base *upo-, and regere ‘to guide, direct; rule, govern’, from PIE base *reg- ‘move in a straight line’.