"The act of pouring out; that which pours out; an overflow, a flood", Mid 19th cent.; earliest use found in The Reader. From out- + pour, after outpour or to pour out.[outpour etymology, outpour origin, 英语词源]
"To pour or send out in or as in a stream", Mid 16th cent.; earliest use found in Thomas Phaer (?1510–1560), translator and physician. From out- + pour.